Rotary electrical machine drive system

ABSTRACT

A rotary electrical machine includes: a rotary electrical machine having a stator and a rotor; and a control device. The rotor includes: a field core having a boss part and claw-shaped magnetic pole parts; a field winding that is wound on the boss part; and permanent magnets that are arranged between the claw-shaped magnetic pole parts. A d-axis magnetic circuit formed by magnetomotive force of the field winding and at least part of first and second magnet magnetic circuits formed by magnetic force of the permanent magnets are shared. When an electrical load is connected to the rotor, a permeance Prt of the d-axis magnetic circuit is set to be smaller than a permeance Pst of the q-axis magnetic circuit. The control device performs phase control such that the rotary electrical machine performs either power running or regeneration.

TECHNICAL FIELD

The present disclosure relates to a rotary electrical machine drive system that is installed in an automobile, truck, or others, for example, and is used as an electric motor or a power generator.

BACKGROUND ART

A vehicle alternating-current power generator includes a Lundell rotor with a field winding and a plurality of claw-shaped magnetic pole parts in which magnetic poles different in polarity are alternately excited by the field winding in a circumferential direction. Such a vehicle alternating-current power generator is known as a conventional rotary electrical machine. PTL 1 discloses a power generator including a magnet-equipped Lundell rotor in which permanent magnets are interposed between the claw-shaped magnetic pole parts to obtain higher output density.

This type of power generator is designed with consideration given to the size of the permanent magnets and the optimization of a boss part, a disc part, and claw-shaped magnetic pole parts of the Lundell rotor core.

Accordingly, the power generator achieves both the improvement of power generation performance and the reduction of back-electromotive force.

PTL 1 describes the mathematical expression derived by determining the relationship between the magnetic flux of a permanent magnet that generates an inflexion point of output characteristics in a power generator and various constants L, W, and θ of claw-shaped magnetic pole pieces. In addition, PTL 1 describes that setting the various constants L, W, and θ would make it possible to decide consistently the residual magnetic flux density Br of the permanent magnets. Accordingly, in the power generator described in PTL 1, the magnetic poles can be set to allow the avoidance of battery overcharge and the achievement of high efficiency and high output at the same time in a universal way even with differences in specifications.

There are known magnet-embedded rotors (IPM rotor) in which permanent magnets are embedded in the outer peripheral portion of a rotor core such that NS poles alternate in the circumferential direction. The IPM rotor has become rapidly widespread due to its high torque, and installed in vehicle power generators, electric motors, and other components.

In recent years, vehicles have been formed in a slant-nose shape and their engine compartments have been reduced in size for reduction of running resistance. Along with this, the installation spaces for vehicle power generators and starters have been minimized. In this case, particular importance is placed on the capability of a starter, high-efficiency power running for assisting a vehicle in high-efficiency operation, and the performance of regenerative operation. Therefore, there has been relatively decreased demand for improvement in only sheer power generation performance, whereas attention has been focused on the power generation, torque, and regenerative ability of power generators for the case where field current becomes large in a short period of time.

CITATION LIST Patent Literature

[PTL 1] JP 4-255451 A

SUMMARY OF THE INVENTION Technical Problem

The power generator with the magnet-equipped Lundell rotor described above has a problem of high back-electromotive force. Accordingly, products with limited back-electromotive force such as vehicle alternating-current power generators include the Lundell rotor with claw-shaped magnetic pole parts described above. However, the power generators with the Lundell rotor have a problem of low power output. The power generators can be enhanced in power generation performance by using magnets designed within the range prescribed by the mathematical expression described in PTL 1. However, there is a need for further improvement in power generation performance.

The present disclosure provides a rotary electrical machine drive system that is further improved in electric torque.

Solution to Problem

FIG. 27 is an equivalent magnetic circuit diagram of a magnet-equipped Lundell rotor. FIG. 28 is an equivalent magnetic circuit diagram of an IPM rotor. In the drawings, Φm represents magnet magnetic flux, Rst represents the magnetic resistance of a stator, AG represents an air gap, Rrt represents the magnetic resistance of a rotor, and Ra represents the magnetic resistance of an air gap in a d-axis circuit. As illustrated in FIG. 27, in the magnet-equipped Lundell rotor, the magnet magnetic flux Φm is branched into two magnetic circuits, that is, a magnetic circuit passing through the boss part of the Lundell rotor core and a magnetic circuit passing through the stator core.

On the other hand, in the IPM rotor, the d-axis circuit is an air gap (a broken-line portion) as illustrated in FIG. 28. Accordingly, the magnetic resistance Ra is very high and inductance Lrt is very low. This causes a difference in torque under an electrical load between the magnet-equipped Lundell rotor and the IPM rotor. That is, when the magnetic resistance Rrt is very high and the inductance Lrt is very low under an electrical load, the magnet-equipped Lundell rotor can output the same degree of torque as the IPM rotor.

The inventor has repeated studies based on the foregoing findings and discovered that it is possible to create the conditions under which the magnet-equipped Lundell rotor can output the same degree of torque as the IPM rotor by using field current If. In the IPM rotor, the magnetic resistance of the field core (rotor core) is high and the magnetic resistance of the stator core is low. Accordingly, the magnet-equipped Lundell rotor can be placed under the same conditions as the IPM rotor by increasing the magnetic resistance value of the field core (Lundell rotor core) to be larger than the magnetic resistance value of the stator core at the time of distribution of the field current If.

The inductance of the rotor is designated as Lrt, the inductance of the stator as Lst, and the magnetic resistance of the magnetic flux flowing in the stator as Rst. When an electrical load is connected to the rotor, the magnetic-equipped Lundell rotor is set to establish Lrt<Lst . . . (Equation 1) or Rrt>Rst . . . (Equation 2). This makes it possible to produce the foregoing conditions. The residual magnetic flux density of the magnet is designated as Br, the cross-sectional area of each magnetic pole of the magnet as Am, the magnetic flux density of the stator as Bs, and the cross-sectional area of the rotor as Ar. At no load, the magnetic-equipped Lundell rotor is set to establish Lrt>Lst, Rrt>Rst, and 2×Br×Am>Bs×Ar (conditions for low back-electromotive force).

However, according to the foregoing (Equation 1) and (Equation 2), the magnetic resistance R cannot be easily measured from a rotary electrical machine as a completed product including a traction motor or a generator. In addition, the inductance L varies depending on the number of windings and fluctuates with the square of the number of turns. Accordingly, it is not appropriate to evaluate the relationship using the inductance L. Therefore, in the subsequent evaluations, permeances Prt and Pst [H] as inverse numbers of the magnetic resistance R were used because they can be easily measured and calculated by an experimental method described later. The relationship between them is expressed as L/N² [H/N²]=1/R [A/wb]=P [H].

Thus, the inventor has found that establishing Prt<Pst under an electrical load on the magnetic-equipped Lundell rotor would allow the rotary electrical machine with biaxial synthetic magnetic flux on a d axis to behave like an IPM rotor.

A first rotary electrical machine drive system as an aspect of the technique of the present disclosure includes: a rotary electrical machine (1) having an annular stator (20) on which an armature winding (25) is wound and a rotor (30) on which a field winding (33) in wound and that is radially opposed to an inner peripheral side of the stator; and a control device (60) that controls electric current supplied to at least one of the field winding and the armature winding to generate torque in the rotor.

The rotor includes: a field core (32) having a cylindrical boss part (321, 321 a, 321 b) on which the field winding is wound and a plurality of claw-shaped magnetic pole parts (323, 323 a, 323 b) that is arranged on the outer peripheral side of the boss part and has magnetic poles different in polarity alternating in a circumferential direction; and permanent magnets (34, 34A) that are arranged with an axis of easy magnetization oriented in the circumferential direction between the circumferentially adjacent claw-shaped magnetic pole parts and have magnetic poles formed to match the alternating polarities of the claw-shaped magnetic pole parts produced by the magnetomotive force of the field winding.

In the first rotary electrical machine drive system, when an electrical load is connected to the rotor, the relationship between a permeance Prt of a d-axis magnetic circuit and a permeance Pst of a q-axis magnetic circuit (37) that is formed from electric current flowing in the armature winding and passes through a q axis shifted from the d axis at an electrical angle of 90° is set to satisfy Pst>Prt.

The control device performs phase control such that the rotary electrical machine performs either power running or regeneration.

According to this configuration, in the first rotary electrical machine drive system, the permanent magnets arranged between the circumferentially adjacent claw-shaped magnetic pole parts form two magnet magnetic circuits, that is, a first magnet magnetic circuit in which the magnetic flux interlinked with the stator flows and a second magnet magnetic circuit in which the magnetic flux passes through the boss part and returns to the rotor. When an electrical load is connected to the rotor, that is, when the field current is distributed to the field winding, the d-axis magnetic circuit is formed in which the magnetic flux formed by the magnetomotive force of the field winding flows through the boss part and the pair of claw-shaped magnetic pole parts of the field core, and the stator core. At this time, the flowing direction of the magnet magnetic flux in, of the two magnet magnetic circuits, the second magnet magnetic circuit in which the magnetic flux passes through the boss part and returns to the rotor is opposite to the flowing direction of the magnetic flux in the d-axis magnetic circuit. Accordingly, the magnetic flux of the magnet magnetic circuit is unlikely to flow due to the magnetic resistance being large. Therefore, in the first rotary electrical machine drive system, the relationship between the permeance Prt of the d-axis magnetic circuit and the permeance Pst of the q-axis magnetic circuit is set to satisfy Pst>Prt. This increases the magnet magnetic flux in, of the first and second magnet magnetic circuits, the first magnet magnetic circuit in which the magnetic flux interlinked with the stator flows. Accordingly, the electric torque generated in the rotor can be significantly improved by the efficient use of the magnet magnetic flux.

The control device in the present disclosure performs phase control such that the rotary electrical machine performs either power running or regeneration. Specifically, when the rotary electrical machine conducts power running (acceleration and speed keeping) or regeneration (simultaneous braking and power generation), the maximum effective torque can be obtained by phase control. In this situation, reluctance torque is generated by applying field-weakening magnetic flux. Applying field-weakening magnetic flux to the d axis means applying the field-weakening magnetic flux to the field core connected to the d axis. That is, at the time of power distribution to the field winding, the saturation of the field core is decreased so that the magnetic force of the permanent magnets is not guided to the stator and is not effectively used. In this case, when the relationship in magnitude between the permeance Prt of the d-axis magnetic circuit and the permeance Pst of the q-axis magnetic circuit is satisfied, the field core is sufficiently saturated. Therefore, the field-weakening magnetic flux is not supplied to the field core so that the reluctance torque can be obtained with little regard to the field-weakening magnetic flux. Accordingly, the performance of power running and regeneration under phase control can be improved in a synergistic manner as compared to the case in which the technique of the present disclosure is applied to operations such as diode rectification and synchronous rectification using only the d axis.

In the present disclosure, the state where the rotor is under an electrical load refers to the state in which the field current If as rated current is distributed to the field winding in a range of 4 to 20 [A] that is usual for performance of a vehicle brush. With an improved structure of the brush, the field current If at that time (for example, 30 [A] or the like) can be used. In a configuration without limitation on the field current If such as a brush-less configuration, the required relationship Pst>Prt can be established by the larger field current If. Even with the known brush, the effect of satisfying the requirement 0.9<As/Ab<1.7 described later would be enormous in the sense of establishing the relationship Pst>Prt.

A second rotary electrical machine drive system as an aspect of the technique of the present disclosure includes: a brushless rotary electrical machine (2) having an annular stator (20) on which an armature winding (25) is wound, a rotor (30) radially opposed to an inner peripheral side of the stator, and a housing (10) that stores the stator and the rotor and has a boss part (17) on which a field winding (33) is wound; and a control device (60) that controls electric current supplied to at least one of the field winding and the armature winding to generate torque in the rotor.

The rotor includes: a field core (52) having a plurality of magnetic pole parts (52 n, 52 s) that is arranged on an outer peripheral side of the field winding and has magnetic poles different in polarity alternating in a circumferential direction; and a permanent magnet (54) that is arranged with an axis of easy magnetization oriented in the circumferential direction between the circumferentially adjacent magnetic pole parts and has a magnetic pole formed to match the alternating polarities of the magnetic pole parts produced by the magnetomotive force of the field winding.

In the second rotary electrical machine drive system, when an electrical load is connected to the rotor, the relationship between a permeance Prt of a d-axis magnetic circuit and a permeance Pst of a q-axis magnetic circuit (57) that is formed from electric current flowing in the armature winding and passes through a q axis shifted from the d axis at an electrical angle of 90° is set to satisfy Pst>Prt.

The control device performs phase control such that the rotary electrical machine performs either power running or regeneration.

According to this configuration, in the second rotary electrical machine drive system, the permanent magnets arranged between the circumferentially adjacent magnetic pole parts form two magnet magnetic circuits, that is, a first magnet magnetic circuit formed by magnetic flux interlinked with the stator flows and a second magnet magnetic circuit that passes through the boss part and returns to the rotor. When an electrical load is connected to the rotor, that is, when the field current is distributed by the control device to the field winding, the d-axis magnetic circuit is formed in which the magnetic flux formed by the magnetomotive force of the field winding flows through the boss part and the pair of magnetic pole parts of the field core, and the stator core. At this time, the flowing direction of the magnet magnetic flux in, of the two magnet magnetic circuits, the second magnet magnetic circuit that passes though the boss part and returns to the rotor is opposite to the flowing direction of the magnetic flux in the d-axis magnetic circuit. Accordingly, the magnetic flux of the magnet magnetic circuit is unlikely to flow due to the magnetic resistance being large. Therefore, in the first rotary electrical machine drive system, the relationship between the permeance Prt of the d-axis magnetic circuit and the permeance Pst of the q-axis magnetic circuit is set to satisfy Pst>Prt. This increases the magnet magnetic flux in, of the first and second magnet magnetic circuits, the first magnet magnetic circuit in which the magnetic flux interlinked with the stator flows. Accordingly, the electric torque generated in the rotor can be significantly improved by the efficient use of the magnet magnetic flux.

In particular, the brushless rotary electrical machine is not subjected to current limitation due to a brush. Accordingly, it is possible to increase the value of the field current If that would be restricted due to the brush. This makes it possible to saturate the field circuit and use efficiently the magnet magnetic force even in the brushless rotary electrical machine. In addition, the independent electrical circuit distributes the field current to the field winding. Accordingly, with regard to centrifugal force as a weak point of the magnet-equipped Lundell rotor, the rear side of the magnetic pole parts is not subjected to the centrifugal force of the electrical circuit. This makes it possible to decrease stress resulting from centrifugal force.

The control device in the present disclosure performs phase control such that the rotary electrical machine performs either power running or regeneration. Specifically, when the rotary electrical machine conducts power running (acceleration and speed keeping) or regeneration (simultaneous braking and power generation), the maximum effective torque can be obtained by phase control. In this situation, reluctance torque is generated by applying field-weakening magnetic flux. Applying field-weakening magnetic flux to the d axis means applying the field-weakening magnetic flux to the field core connected to the d axis. That is, at the time of power distribution to the field winding, the saturation of the field core is decreased so that the magnetic force of the permanent magnets is not guided to the stator and is not effectively used. In this case, when the relationship in magnitude between the permeance Prt of the d-axis magnetic circuit and the permeance Pst of the q-axis magnetic circuit is satisfied, the field core is sufficiently saturated. Therefore, the field-weakening magnetic flux is not supplied to the field core so that the reluctance torque can be obtained with little regard to the field-weakening magnetic flux. Accordingly, the performance of power running and regeneration under phase control can be improved in a synergistic manner as compared to the case in which the technique of the present disclosure is applied to operations such as diode rectification and synchronous rectification using only the d axis.

A third rotary electrical machine drive system as an aspect of the present disclosure includes: a rotary electrical machine (1) having an annular stator (20) on which an armature winding (25) is wound and a rotor (30) on which a field winding (33) in wound and that is radially opposed to an inner peripheral side of the stator; and a control device (60) that controls electric current supplied to at least one of the field winding and the armature winding to generate torque in the rotor.

The rotor includes: a field core (32) having a cylindrical boss part (321, 321 a, 321 b) and a plurality of claw-shaped magnetic pole parts (323, 323 a, 323 b) that are arranged on an outer peripheral side of the boss part and have magnetic poles different in polarity alternating in a circumferential direction; a field winding (33) that is wound on the outer peripheral side of the boss part to generate a magnetomotive force by energization; and permanent magnets (34, 34A) that are arranged with an axis of easy magnetization oriented in the circumferential direction between the circumferentially adjacent claw-shaped magnetic pole parts and have magnetic poles formed to match the alternating polarities of the claw-shaped magnetic pole parts produced by the magnetomotive force of the field winding.

In the present disclosure, the surface area of the outer peripheral surface of the claw-shaped magnetic pole part is designated as As, and the axially extending iron core cross-sectional area of a pair of NS poles of the boss part as Ab. In this case, in the third rotary electrical machine drive system, the relationship between the surface area As and the cross-sectional area Ab is set within a range of 0.9<As/Ab<1.7.

The control device performs phase control such that the rotary electrical machine performs either power running or regeneration.

According to this configuration, in the third rotary electrical machine drive system, the relationship between the surface area As of the outer peripheral surface of the claw-shaped magnetic pole part and the axially extending iron core cross-sectional area Ab of a pair of NS poles of the boss part is set within the range of 0.9<As/Ab<1.7. Accordingly, the magnet magnetic flux can be increased in, of the magnet magnetic circuits formed by the permanent magnets arranged between the circumferentially adjacent claw-shaped magnetic pole parts, the magnet magnetic circuit in which the magnet magnetic flux interlinked with the stator flows. This improves significantly the electric torque by the efficient use of the magnet magnetic flux. The permanent magnets arranged between the claw-shaped magnetic pole parts are conventionally used for the purposes of rectification of magnetic flux and prevention of leakage of magnetic flux. In contrast, in the present disclosure, the permanent magnets arranged between the claw-shaped magnetic pole parts are used like permanent magnets in an IPM rotor. This achieves increase of magnetic flux rather than prevention of leakage of a magnetic flux. That is, the permanent magnets can act as a source for torque increase or a source for power increase.

The control device in the present disclosure performs phase control such that the rotary electrical machine performs either power running or regeneration. Specifically, when the rotary electrical machine conducts power running (acceleration and speed keeping) or regeneration (simultaneous braking and power generation), the maximum effective torque can be obtained by phase control. In this situation, reluctance torque is generated by applying field-weakening magnetic flux. Applying field-weakening magnetic flux to the d axis means applying the field-weakening magnetic flux to the field core connected to the d axis. That is, at the time of power distribution to the field winding, the saturation of the field core is decreased so that the magnetic force of the permanent magnets is not guided to the stator and is not effectively used. In this case, when the relationship in magnitude between the permeance Prt of the d-axis magnetic circuit and the permeance Pst of the q-axis magnetic circuit is satisfied, the field core is sufficiently saturated. Therefore, the field-weakening magnetic flux is not supplied to the field core so that the reluctance torque can be obtained with little regard to the field-weakening magnetic flux. Accordingly, the performance of power running and regeneration under phase control can be improved in a synergistic manner as compared to the case in which the technique of the present disclosure is applied to operations such as diode rectification and synchronous rectification using only the d axis.

A fourth rotary electrical machine drive system as an aspect of the technique of the present disclosure includes: a brushless rotary electrical machine (2) having an annular stator (20) on which an armature winding (25) is wound, a rotor (50) radially opposed to an inner peripheral side of the stator, and a housing (10) that stores the stator and the rotor and has a boss part (17) on which a field winding (53) is wound; and a control device (60) that controls electric current supplied to at least one of the field winding and the armature winding to generate torque in the rotor.

The rotor includes: a field core (52) having a plurality of magnetic pole parts (523 h, 523 i) that is arranged on an outer peripheral side of the field winding and has magnetic poles different in polarity alternating in a circumferential direction; and permanent magnets (54) that are arranged with an axis of easy magnetization oriented in the circumferential direction between the circumferentially adjacent magnetic pole parts and have magnetic poles formed to match the alternating polarities of the magnetic pole parts produced by the magnetomotive force of the field winding.

In the present disclosure, the surface area of the outer peripheral surface of the magnetic pole part is designated as As, and the axially extending iron core cross-sectional area of a pair of NS poles of the boss part as Ab. In this case, in the fourth rotary electrical machine drive system, the relationship between the surface area As and the cross-sectional area Ab is set within a range of 0.9<As/Ab<1.7.

The control device performs phase control such that the rotary electrical machine performs either power running or regeneration.

According to this configuration, in the fourth rotary electrical machine drive system, the relationship between the surface area As of the outer peripheral surface of the magnetic pole part and the axially extending iron core cross-sectional area Ab of a pair of NS poles of the boss part is set within the range of 0.9<As/Ab<1.7. Accordingly, the magnet magnetic flux can be increased in, of the magnet magnetic circuits formed by the permanent magnets arranged between the circumferentially adjacent magnetic pole parts, the magnet magnetic circuit in which the magnet magnetic flux interlinked with the stator flows. This improves significantly the power generation performance by the efficient use of the magnet magnetic flux. The permanent magnets arranged between the magnetic pole parts are conventionally used for the purposes of rectification of magnetic flux and prevention of leakage of magnetic flux. In contrast, in the present disclosure, the permanent magnets arranged between the magnetic pole parts are used like permanent magnets in an IPM rotor. This achieves increase of magnetic flux rather than prevention of leakage of magnetic flux. That is, the permanent magnets can act as a source for torque increase or a source for power increase.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating a configuration of a rotary electrical machine drive system according to a first embodiment;

FIG. 2 is a perspective view of a rotor according to the first embodiment;

FIG. 3 is a diagram illustrating various dimensions of a field core according to the first embodiment;

FIG. 4 is a diagram illustrating various dimensions of the field core according to the first embodiment;

FIG. 5 is a diagram illustrating various dimensions of a claw-shaped magnetic pole part of the field core according to the first embodiment;

FIG. 6 is a diagram illustrating various dimensions of the field core according to the first embodiment;

FIG. 7 is a diagram illustrating a d-axis magnetic circuit and a q-axis magnetic circuit formed in a rotary electrical machine according to the first embodiment;

FIG. 8 is a diagram illustrating a flow of a magnetic flux on the field core side of the d-axis magnetic circuit formed in the rotary electrical machine according to the first embodiment;

FIG. 9 is a graph illustrating saliency ratios ρ of a Lundell rotor and an IPM rotor;

FIG. 10 is a diagram illustrating two magnetic circuits formed by permanent magnets in the rotary electrical machine according to the first embodiment;

FIG. 11 is a circuit connection diagram of an inverter according to the first embodiment;

FIG. 12 is a diagram for describing a method for measuring permeances in the first embodiment;

FIG. 13 is a diagram for describing the method for measuring permeances in the first embodiment;

FIG. 14 is a graph illustrating measurement results of permeances in a rotary electrical machine according to a first comparative example;

FIG. 15 is a graph illustrating measurement results of permeances in the rotary electrical machine according to the first embodiment;

FIG. 16 is a diagram for describing the method for measuring a permeance in the rotor in the first embodiment;

FIG. 17 is a diagram for describing the method for measuring a permeance in the rotor in the first embodiment;

FIG. 18 is a diagram for describing the method for measuring a permeance in a stator in the first embodiment;

FIG. 19 is a diagram for describing the method for measuring a permeance in the stator in the first embodiment;

FIG. 20 is a graph illustrating the relationship between the ratio (As/Ab) of a claw-shaped magnetic pole part surface area As to a boss part cross-sectional area Ab and the amount of an interlinked magnetic flux under an electrical load on the stator;

FIG. 21 is a graph illustrating the relationship between the ratio (Db/Dr) of a boss part outer diameter Db to a rotor outer diameter Dr and the amount of an interlinked magnetic flux under an electrical load on the stator;

FIG. 22 is a diagram illustrating the relationship between the ratio (As/Ab) of the claw-shaped magnetic pole part surface area As to the boss cross-sectional area Ab and the ratio (Db/Dr) of the boss part outer diameter Db to the rotor outer diameter Dr;

FIG. 23 is a voltage vector diagram of a rotary electrical machine produced in a conventional dimension range and permeance relationship;

FIG. 24 is a voltage vector diagram of a rotary electrical machine produced in the dimension range and permeance relationship of the present disclosure;

FIG. 25 is a diagram describing field-weakening control with one d axis;

FIG. 26 is a diagram describing field-weakening control with two d axes;

FIG. 27 is an equivalent magnetic circuit diagram of a magnet-equipped Lundell rotor;

FIG. 28 is an equivalent magnetic circuit diagram of an IPM rotor;

FIG. 29 is a schematic diagram illustrating a configuration of a rotary electrical machine drive system according to a second embodiment, which corresponds to cross sections of FIGS. 30 and 32 taken along line XXIX-XXIX;

FIG. 30 is a perspective view of the rotary electrical machine according to the second embodiment;

FIG. 31 is a perspective view of a rotor and a cover portion according to the second embodiment;

FIG. 32 is a front view of the rotor according to the second embodiment;

FIG. 33 is a front view of an iron core of the rotor according to the second embodiment;

FIG. 34 is a front view of an N pole core and an S pole core of the rotor according to the second embodiment;

FIG. 35 is a diagram illustrating two magnetic circuits formed by permanent magnets in the rotary electrical machine according to the second embodiment;

FIG. 36 is a diagram illustrating a d-axis magnetic circuit and a q-axis magnetic circuit formed in the rotary electrical machine according to the second embodiment;

FIG. 37 is an axial cross-sectional view of a pole core according to a third embodiment;

FIG. 38 is a perspective view of a pole core according to a fourth embodiment;

FIG. 39 is a perspective view of a pole core according to a fifth embodiment;

FIG. 40 is a perspective view of a pole core according to a sixth embodiment;

FIG. 41 is an axial cross-sectional view of a pole core according to a seventh embodiment;

FIG. 42 is an axial cross-sectional view of a pole core according to an eighth embodiment;

FIG. 43 is a perspective view of a pole core according to a ninth embodiment;

FIG. 44 is a perspective view of a pole core according to a tenth embodiment;

FIG. 45 is an axial cross-sectional view of a pole core according to an eleventh embodiment; and

FIG. 46 is a diagram illustrating arrangement of permanent magnets according to a first modification example.

DESCRIPTION OF EMBODIMENTS

Embodiments of a rotary electrical machine drive system as an aspect of the technique of the present disclosure will be specifically described with reference to the drawings.

First Embodiment

A rotary electrical machine drive system according to a first embodiment will be described with reference to FIGS. 1 to 26. The rotary electrical machine drive system according to the present embodiment is a drive system for a vehicle alternating-current power generator that is installed in a vehicle and allows the selectively use of the functions of a power generator and an electrical machine.

<Overall Configuration of the Rotary Electrical Machine Drive System>

The rotary electrical machine drive system in the present embodiment includes, as illustrated in FIG. 1, a rotary electrical machine 1 having a housing 10, a stator 20, a rotor 30, and other components, and a control device 60 having an excitation circuit 61, an inverter 63, a controller 67, and other components.

The housing 10 of the rotary electrical machine 1 includes a hollow cylindrical portion 11 and a disc-shaped cover portion 12. The cover portion 12 is fitted and fixed to an opening at one end of the cylindrical portion 11. The stator 20 has an annular stator core 21 and an armature winding 25. The stator core 21 has pluralities of slots 22 and teeth 23 (see FIG. 7) aligned in the circumferential direction. The armature winding 25 is wound on the slots 22 of the stator core 21. The armature winding 25 is formed from three-phase (U phase, V phase, and W phase) windings U, V, and W as illustrated in FIG. 11. Each of the phase windings U, V, and W has one end star-connected to form a neutral point and the other end connected to an output terminal U1, V1, or W1 of the inverter 63. In the stator 20, the outer peripheral surfaces of the stator cores 21 are fixed to the inner peripheral surface of the cylindrical portion 11 of the housing 10.

The rotor 30 has a rotation shaft 31, a Lundell field core 32, a field winding 33, and a plurality of permanent magnets 34. The rotation shaft 31 is rotatably supported on the housing 10 via a pair of bearings 14. The field core 32 includes a pair of pole cores 32 a and 32 b that is fitted and fixed together on the outer periphery of the rotation shaft 31. The field winding 33 is wound on the outer peripheral side of a boss part 321 of the field core 32. The permanent magnets 34 are arranged between circumferentially adjacent claw-shaped magnetic pole parts 323 of the field core 32.

The rotor 30 is rotatably provided with the field core 32 radially opposed to the inner peripheral side of the stator 20. The rotor 30 is rotationally driven by an engine (not illustrated) installed in the vehicle via a pulley and a driving force transfer member (not illustrated) fixed to the back end of the rotation shaft 31 (the right end of FIG. 1). The rotor 30 has a pair of slip rings 41 and a pair of brushes 42 as a device for supplying electrical power from an excitation circuit 61 described later to the field winding 33 at the front end of the rotation shaft 31 (the left end of FIG. 1). The pair of slip rings 41 is fitted and fixed to the outer peripheral surface of the rotation shaft 31. The pair of brushes 42 is arranged with the radially inner front ends pressed on the surfaces of the slip rings 41 in a slidable manner.

The field core 32 includes the first pole core 32 a and the second pole core 32 b as illustrated in FIGS. 1 and 2. The first pole core 32 a is fixed to the front side of the rotation shaft 31 (the left side of FIG. 1). The second pole core 32 b is fixed to the rear side of the rotation shaft 31 (the right side of FIG. 1). The first pole core 32 a includes a cylindrical first boss part 321 a, a first disc part 322 a, and first claw-shaped magnetic pole parts 323 a. The first boss part 321 a flows a field magnetic flux in the axial direction on the radially inside of the field winding 33. The first disc part 322 a extends the radially outward from the axial front end of the first boss part 321 a at a predetermined circumferential pitch to permit the field magnetic flux to flow in the radial direction. The first claw-shaped magnetic pole parts 323 a axially extend from the front end of the first disc part 322 a on the outer peripheral side of the first boss part 321 a to surround the field winding 33 and exchange magnetic flux with the stator core 21.

The second pole core 32 b is identical in shape to the first pole core 32 a. However, the second pole core 32 b has a second boss part 321 b, a second disc part 322 b, and second claw-shaped magnetic pole parts 323 b. The first and second pole cores 32 a and 32 b are formed from soft magnetic bodies.

The field core 32 in the present embodiment is formed from two kinds of materials different in saturation flux density Bs. Specifically, the claw-shaped magnetic pole parts 323 are formed from a material high in saturation flux density Bs. Other than the claw-shaped magnetic pole parts 323, the boss part 321 and the disc part 322 are formed from a material low in saturation flux density Bs. Examples of a material high in saturation flux density Bs include a material with about 0.1% carbon such as S10C (prescribed by Japanese Industrial Standards). Examples of a material low in saturation flux density Bs include a material with a large amount of carbon such as S45C (prescribed by Japanese Industrial Standards). For reference, SUS430 (prescribed by Japanese Industrial Standards) and electromagnetic steel sheets are lower in saturation flux density Bs than S10C.

The material low in saturation flux density Bs used here is higher in magnetic permeability than the material high in saturation flux density Bs. Examples of a material high in magnetic permeability include permalloy. Iron mixed with nickel cobalt is not suitable because of its high saturation flux density Bs.

The first pole core 32 a and the second pole core 32 b are assembled together such that the first claw-shaped magnetic pole parts 323 a and the second claw-shaped magnetic pole parts 323 b are opposed to each other in a staggered pattern, and the axial rear end surface of the first pole core 32 a and the axial front end surface of the second pole core 32 b face each other. Accordingly, the first claw-shaped magnetic pole parts 323 a of the first pole core 32 a and the second claw-shaped magnetic pole parts 323 b of the second pole core 32 b are alternately arranged in the circumferential direction. The first and second pole cores 32 a and 32 b have eight each claw-shaped magnetic pole parts 323. In the present embodiment, the Lundell rotor core is provided with 16 poles (eight N poles and eight S poles).

In the first embodiment, as illustrated in FIG. 3, the outer diameter of the boss part 321 of the field core 32 is designated as Db (hereinafter, also called “boss part outer diameter Db”) and the outer diameter of the rotor 30 (the field core 32) as Dr (hereinafter, also called “rotor outer diameter Dr”). In the present embodiment, the relationship between the boss part outer diameter Db and the rotor outer diameter Dr is set within a range of 0.46<Db/Dr<0.53. The relationship between the boss part outer diameter Db and the rotor outer diameter Dr will be described later in detail.

In addition, the surface area of the outer peripheral surface of the claw-shaped magnetic pole part 323 is designated as As (hereinafter, also called “claw-shaped magnetic pole part surface area As”) and the axially extending iron core cross-sectional area of a pair of NS poles of the boss part 321 (the area of a cross section vertical to the direction in which the iron core extends (the axial direction) as Ab (hereinafter, also called “boss part cross-sectional area Ab”). In the present embodiment, the relationship between the claw-shaped magnetic pole part surface area As and the boss part cross-sectional area Ab is set within a range of 0.9<As/Ab<1.7. The boss part cross-sectional area Ab can be expressed as A/P where A represents the total cross-sectional area of the cylindrical boss part 321 and P represents the number of pole pairs in the rotary electrical machine as illustrated in FIGS. 3 and 4.

Next, the claw-shaped magnetic pole part surface area As will be defined. In the present embodiment, as illustrated in FIGS. 5 and 6, the peripheral width of the root of the claw-shaped magnetic pole part 323 or the disc part 322 is designated as Wrr, the circumferential width of the front end of the claw-shaped magnetic pole part 323 as Wte, and the axial height of the claw-shaped magnetic pole part 323 as Ht. On radially opposed surfaces of the rotor 30 and the stator 20, the area in which the axial length of the stator core 21 and the axial thickness of the disc part 322 radially overlap is designated as disc guide Hdg. No large differences in dimensions are caused by cut portions, rounded portions, and chamfered portions designed in the disc part 322, the claw-shaped magnetic pole parts 323, and the stator core 21 for the purposes of magnet insertion and strength enhancement. In this case, the claw-shaped magnetic pole part surface area As is equal to (Wte+Wrr)×Ht/2+Hdg×Wrr. In the present disclosure, the circumferential width W is measured by linear distance with no consideration given to curvature. The relationship between the claw-shaped magnetic pole part surface area As and the boss part cross-sectional area Ab will be described later in detail.

The field winding 33 is wound in the state isolated from the field core 32 on the outer peripheral sides of the first and second boss parts 321 a and 321 b of the first and second pole cores 32 a and 32 b, and is surrounded by the first and second claw-shaped magnetic pole parts 323 a and 323 b. The field winding 33 generates a magnetomotive force in the boss part 321 by distribution of the field current If from the excitation circuit 61 of the control device 60. Accordingly, magnetic poles different in polarity are formed in the first claw-shaped magnetic pole parts 323 a and the second claw-shaped magnetic pole parts 323 b of the first and second pole cores 32 a and 32 b. That is, the first claw-shaped magnetic pole parts 323 a are magnetized at one of the NS poles, and the second claw-shaped magnetic pole parts 323 b are magnetized at the other of the NS poles.

Accordingly, as illustrated in FIGS. 7 and 8, a d-axis magnetic circuit 36 (indicated by a broken line in FIGS. 7 and 8) is formed by the magnetic flux passing through the boss part 321 and the pair of first and second claw-shaped magnetic pole parts 323 a and 323 b of the field core 32. The d-axis magnetic circuit 36 enters from the d-axis tooth 23 of the stator core 21 into the first claw-shaped magnetic pole part 323 a of the field core 32 and passes through the first disc part 322 a, the first boss part 321 a, the second boss part 321 b, the second disc part 322 b, and the second claw-shaped magnetic pole part 323 b. Then, after returning to the stator core 21 from the tooth 23 shifted by one magnetic pole of the stator core 21, the d-axis magnetic circuit 36 passes through a back core 24 and reaches the d-axis tooth 23 shifted by one magnetic pole. The d-axis magnetic circuit 36 is a magnetic circuit that generates a back-electromotive force of the rotor 30.

Current flows into the armature winding 25 by the d-axis magnetic circuit 36 and the magnetic flux interlinked with the stator 20 in a first magnet magnetic circuit 38 described later. This forms a q-axis magnetic circuit 37 (indicated by a solid line in FIG. 7). The q-axis magnetic circuit 37 is formed by the magnetic flux passing through a q axis shifted from the d axis of the stator core 21 at an electrical angle of 90°. In the present embodiment, the relationship between a permeance Prt of the d-axis magnetic circuit 36 and a permeance Pst of the q-axis magnetic circuit 37 is set to satisfy Pst>Prt under an electrical load on the rotor 30.

In this example, the state where the rotor 30 is under an electrical load refers to the state in which the field current If as rated current is distributed to the field winding 33 in a range of 4 to 20 [A] that is usual for performance of a vehicle brush. With an improved structure of the brush, the field current If at that time (for example, 30 [A] or the like) can be used. In a configuration without limitation on the field current If such as a brush-less configuration, the required relationship Pst>Prt can be established by the larger field current If. Even using the known brush, in the sense of establishing the relationship Pst>Prt, the effect of setting the relationship between the boss part outer diameter Db and the rotor outer diameter Db within the range of 0.46<Db/Dr<0.53 and the effect of setting the relationship between the claw-shaped magnetic pole part surface area As and the boss part cross-sectional area Ab within the range of 0.9<As/Ab<1.7 are very significant.

The ratio of the permeance Prt of the d-axis magnetic circuit 36 to the permeance Pst of the q-axis magnetic circuit 37 is set to Pst:Prt=2n:1 (n is a real number of 1 or larger). In this example, the ratio (Lq/Ld) of a q-axis inductance Lq to a d-axis inductance Ld is designated as saliency ratio ρ. As illustrated in FIG. 9, the saliency ratio ρ of a conventional Lundell rotor is ρ≈1, and the saliency ratio ρ of a conventional IPM rotor is ρ≈2 to 4. In contrast, in the present embodiment, the permeance ratio of the d-axis magnetic circuit 36 to the q-axis magnetic circuit 37 is set as described above. Accordingly, the operation mode of the Lundell rotor 30 under an electrical load can be brought closer to that of the IPM rotor. In addition, the saliency ratio ρ can be set to 2 or larger. Methods for measuring the permeance Prt of the d-axis magnetic circuit 36 and the permeance Pst of the q-axis magnetic circuit 37 will be described later in detail.

As illustrated in FIGS. 2, 3, and 8, there are formed longitudinally extending clearances in an axially oblique direction between the first claw-shaped magnetic pole parts 323 a and the second claw-shaped magnetic pole parts 323 b that are alternately arranged in the circumferential direction. One permanent magnet 34 is arranged in each clearance. Each of the permanent magnets 34 has a rectangular solid shape and has an axis of easy magnetization oriented in the circumferential direction. Each of the permanent magnets 34 is held by the first and second claw-shaped magnetic pole parts 323 a and 323 b while the magnetic pole parts of the permanent magnet 34 on the both circumferential sides are in abutment with the peripheral side surfaces of the first and second claw-shaped magnetic pole parts 323 a and 323 b. That is, each of the permanent magnets 34 has magnetic poles formed to match the alternating polarities of the first and second claw-shaped magnetic pole parts 323 a and 323 b produced by the magnetomotive force of the field winding 33.

In the present embodiment, the permanent magnets 34 are arranged in this manner. As illustrated in FIG. 10, each of the permanent magnets 34 has the first and second magnet magnetic circuits 38 and 39. The first magnet magnetic circuit (indicated by a one-dot chain line in FIG. 10) 38 is a magnetic circuit with, of magnet magnetic fluxes, the magnetic flux interlinked with the stator 20. The second magnet magnetic circuit (indicated by a double line in FIG. 10) 39 is a magnetic circuit with, of the magnet magnetic fluxes, the magnetic flux passing through the boss part 321 a and the disc parts 322 a and 322 b and returning to the rotor 30. From the viewpoint of these magnetic fluxes, the second magnet magnetic circuit 39 passing through the boss part 321 is a magnetic circuit with the magnet magnetic flux ineffective for the stator 20, whereas the first magnet magnetic circuit 38 is a magnetic circuit with the magnet magnetic flux interlinked with the stator 20 and forming a back-electromotive force and torque.

In this case, the first magnet magnetic circuit 38 and the d-axis magnetic circuit 36 share the magnetic circuit from the second claw-shaped magnetic pole part 323 b through the stator 20 to the first claw-shaped magnetic pole part 323 a. The second magnet magnetic circuit 39 and the d-axis magnetic circuit 36 share the magnetic circuit that corresponds to the first and second boss parts 321 a and 321 b and the first and second disc parts 322 a and 322 b of the rotor 30.

In the present embodiment, the axially extending iron core cross-sectional area of a pair of NS poles of the boss part 321 is designated as Ab and the magnetic flux density of the boss part 321 with a magnetic field of 5000 [A/m] as B50. In addition, the residual magnetic flux density of the permanent magnet 34 arranged between the claw-shaped magnetic pole parts 323 is designated as Br, and the cross-sectional area of the surface of the permanent magnet 34 constituting the magnetic pole as Am. In the present embodiment, the foregoing elements are set to satisfy the relationship 2×Br [T]×Am [mm²]<B50 [T]×Ab [mm²]. The settings for this relationship will be described later in detail.

The excitation circuit 61 of the control device 60 supplies the field current If from a power source B1 to the field winding 33 via the pair of brushes 42 and the pair of slip rings 41. The excitation circuit 61 is formed from a switching element (not illustrated) including an insulated-gate bipolar transistor (IGBT) or the like, for example. The turning on and off of the switching element of the excitation circuit 61 is controlled by the controller (ECU) 67.

The inverter 63 supplies an armature current Ia to the armature winding 25. As illustrated in FIG. 11, the inverter 63 has three upper arm elements 64 and three lower arm elements 64. Each of the arm elements 64 includes an insulated-gate bipolar transistor (IGBT) (hereinafter, also called “IGBT 64 a”) and a reflux diode 64 b. A smoothing capacitor 65 smooths an alternating current on the power source B2 side.

The inverter 63 has the same function as that of a publicly known PWM control inverter. In the inverter 63, the IGBTs 64 a are repeatedly turned on and off according to pulse width modulation (PWM) signals as control output signals of V/F control and vector control to generate a three-phase alternating voltage. The IGBTs 64 a of the upper and lower arm elements 64 are set to operate reversely so that they are not turned on at the same time. The turning on and off of the IGBTs 64 a of the inverter 63 are controlled by the controller (ECU) 67 based on information from a position sensor 66 that detects the rotation position of the rotor 30.

The thus configured control device 60 controls electric current supplied to the field winding 33 and the armature winding 25 to generate electric torque of a necessary magnitude in the rotor 30. The control device 60 performs phase control for field weakening such that the rotary electrical machine 1 performs either power running or regeneration. Accordingly, in the present embodiment, the dimensions of the rotor 30 and the relationship between permeances in the magnetic circuits are set as described above. This makes it possible to generate extremely favorable electric power and torque.

In the thus configured rotary electrical machine drive system of the present embodiment, when a rotational force from the engine is transferred via a driving force transfer member or the like, the rotor 30 rotates together with the rotation shaft 31 in a predetermined direction. In this state, the rotary electrical machine drive system applies an exciting voltage from the excitation circuit 61 to the field winding 33 of the rotor 30 via the slip rings 41 and the brushes 42. Accordingly, the first and second claw-shaped magnetic pole parts 323 a and 323 b of the field core 32 are excited to form alternately NS magnetic poles along the rotational circumferential direction of the rotor 30.

In synchronization with this, in the rotary electrical machine drive system, the stator 20 is excited based on a drive current supplied from the inverter 63 of the control device 60 to the armature winding 25. As a result, an electric torque (including motive power) is generated by the action of excitation to rotate the rotor 30. At this time, the control device 60 performs field weakening control to generate a larger electric torque. The generated electric torque is output from the rotor 30 and the rotation shaft 31 to a drive portion such as an axle, for example, via a driving force transfer member. At this time, to accelerate the rotation of the rotor 30 or keep the rotation speed of the rotor 30, the rotary electrical machine 1 operates as an electric motor to perform power running.

In addition, in the rotary electrical machine drive system, when a rotational force from the engine is transferred via a driving force transfer member or the like so that the rotor 30 rotates together with the rotation shaft 31 in a predetermined direction, no drive current is supplied from the inverter 63 to the armature winding 25 but an excitation voltage is applied from the excitation circuit 61 to the field winding 33 of the rotor 30 via the slip rings 41 and the brushes 42. As a result, the first and second claw-shaped magnetic pole parts 323 a and 323 b of the field core 32 are excited to form alternately the NS magnetic poles along the rotational circumferential direction of the rotor 30.

Accordingly, in the rotary electrical machine drive system, a rotating magnetic field is applied to the armature winding 25 of the stator 20 to generate an alternating-current electromotive force in the armature winding 25. The alternating-current electromotive force (regenerative power) generated in the armature winding 25 passes through the inverter 63 and is rectified to a direct current, and then is taken from the output terminal and charged into the power source B2. At this time, to conduct braking and power generation at the same time, the rotary electrical machine 1 acts as a power generator to perform regeneration.

In the rotary electrical machine 1 configured as described above, the boss parts 321 a and 321 b of the pole cores 32 a and 32 b are narrower than the conventional ones or the disc parts 322 a and 322 b of the pole cores 32 a and 32 b are thinner than the conventional ones. Accordingly, in the rotary electrical machine 1, the field winding 33 can be wound an increased number of times by the narrowing of the boss parts 321 a and 321 b or the thinning of the disc parts 322 a and 322 b. Otherwise, in the rotary electrical machine 1, the wire material for the field winding 33 can be thickened by the narrowing of the boss parts 321 a and 321 b or the thinning of the disc parts 322 a and 322 b. As a result, in the rotary electrical machine 1, the volume ratio of the field winding 33 increases in the rotor 30 including the field core 32 and the field winding 33. The field winding 33 is formed from a wire material made of copper or the like, which is higher in thermal conductivity than the field core 32 made of iron or the like. That is, in the rotor 30 including the field core 32 and the field winding 33, the volume ratio of the field winding 33 higher in thermal conductivity than the field core 32 increases. Accordingly, in the rotary electrical machine 1, the rotor 30 can be improved in heat dissipation. Thus, the rotary electrical machine 1 allows the rotor 30 to be cooled by air.

In addition, in the rotary electrical machine 1, the total amount of the material for the pole cores 32 a and 32 b can be decreased by the narrowing of the boss parts 321 a and 321 b or the thinning of the disc parts 322 a and 322 b. Therefore, welding pressure necessary for forge processing can be reduced. Accordingly, although the boss part 321 is separately formed in the present embodiment, the boss part 321 and the disc parts 322, and also the claw-shaped magnetic pole parts 323 can be integrally molded in an easy manner.

<About the Setting of the Relationship 2×Br [T]×Am [mm²]<B50 [T]×Ab [mm²]>

The rotary electrical machine drive system in the present disclosure is a vehicle rotary electrical machine that is connected to a power source of 12 to 48 [V], or 6 to 60 [V] including a range of tolerance, and can function as an alternator or a starter. Accordingly, in the rotary electrical machine drive system of the present disclosure, the back-electromotive force is not to be large unlike in an IPM rotor. A usual group of products with a rotor diameter of about 70 to 120 [mm] and a rotor axial length of about 30 to 80 [mm] generates a back-electromotive force of 200 to 300 [V] in an IPM rotor. In this situation, there is a concern that overcharging of a 12 to 48-[V] battery may occur, or there may be some negative influence of high voltage on other electric components even in the absence of overcharge. Accordingly, the back-electromotive force cannot be sufficiently lowered.

To solve this problem, in the rotary electrical machine drive system of the present disclosure, the relationship 2×Br [T]×Am [mm²]<Bs [T]×Ab [mm²] is satisfied. Otherwise, the magnetic flux cannot be sufficiently lowered. The symbol Bs [T] represents the saturation flux density of the field core 32. The Br [T] cannot be sufficiently absorbed without sufficiently high relative permeability. The saturation flux density Bs [T] of the field core 32 is employed here as the value of B50 [T] that is usually used.

A usual 12 to 48-[V] product has a magnetomotive force of about 2500 [AT] applied to the field core 32. Thus, the thickness (mm) and holding capacity Hc (A/m) of the permanent magnets 34 are designed at a safety ratio of about 5000 [A] or more. The Br value and the Hc value vary somewhat depending on the temperature assumed by the designer. However, the range of 5000 [A] needs to fall within a temperature range of −40 to 160 [° C.] in which the product is supposed to be used. The present disclosure specified by the permanent magnets 34 designed at about 5000 [A] and the value of B50 as the magnetic flux density at 5000 [A] is very high in reliability. Prior to this, the relative magnetic permeability is as sufficiently high as 30 or more. The permanent magnets 34 with the residual magnetic flux density Br are connected to air gaps for insertion or air gaps for holding an air gap distance of about 1 [mm] at maximum in the field core 32 and are placed with a sufficiently high permeance in the magnetic circuit. Accordingly, the effective magnetic flux density Bd [T] can be sufficiently considered to be equal to Br [T].

<Methods for Measuring the Permeances>

Methods for measuring the permeance Prt of the d-axis magnetic circuit 36 and the permeance Pst of the q-axis magnetic circuit 37 will be described. FIGS. 12 and 13 schematically illustrate the N pole and S poles of the rotor 30, the field winding 33, and the stator 20. At the time of measurement, a direct-current power source is connected to the field winding 33. In addition, a measurement instrument with an LCR meter and a voltage probe is connected to any of the terminals of the conducting stator 20. The measurement instrument may be any instrument capable of measuring a voltage such as an oscilloscope. Accordingly, the measurement instrument can be a combination of a voltage probe and any voltmeter.

In this case, the stator 20 and the rotor 30 are preferably in the positional relationship in which the stator 20 is not subjected to field weakening excitation with respect to the center of the d axis of the rotor 30 but is subjected to excitation toward the q axis. This is because, in the case of field weakening excitation, applying field weakening to the field circuit of the rotor 30 might not allow correct measurement. As a matter of course, at an electrical angle of about 15° or less at which field weakening is less effective, the effect of field weakening is sin 15°≈0.25 in excitation magnetic flux. Accordingly, a certain degree of reliable data can be obtained in the positional relationship with the maximum inductance within a range of electrical angle ±15° from the energization of the q axis. For consideration excluding magnet magnetic flux, the measurement is preferably made without the permanent magnets 34 or with the permanent magnets 34 sufficiently demagnetized.

FIG. 14 is a graph illustrating the measurement results of permeances in a rotary electrical machine according to a first comparative example. FIG. 15 is a graph illustrating the measurement results of permeances in the rotary electrical machine according to the first embodiment. The first comparative example is targeted at a rotary electrical machine prescribed by the mathematical expression described in PTL 1. As illustrated in FIG. 14, in the first comparative example, the permeance of the rotor 30 is higher at no load. However, as the field current of the rotor 30 is increased, the permeance of the rotor 30 becomes equal to that of the stator 20. At no load, the stator 20 is lower in permeance than the rotor 30 due to the magnetic barrier on the q axis and the magnets. That is, the magnetic flux is unlikely to flow into the stator 20 to prevent overcharge resulting from a back-electromotive force at no load. Although the first comparative example and the present embodiment are identical in this point, the permeance of the stator 20 is higher than that of the rotor 30 under an electrical load. That is, the magnetic flux is likely to flow into the stator 20, which makes it possible to increase the back-electromotive force under an electrical load and obtain high main magnetic flux torque (main magnetic flux (magnet magnetic flux+field flux)×current value). In this case, Tm [Nm]=Ψ×Iq where Tm represents magnet torque, Ψ represents main magnetic flux, and Iq represents q-axis current.

Next, a method for calculating the permeance of the rotor 30 will be described with reference to FIGS. 16 and 17. The field winding 33 is caused to generate a magnetic field and excite a field circuit (the d-axis magnetic circuit 36) by a direct-current power source. At this time, the rotor 30 is rotated to generate a back-electromotive force. The rotor 30 is operated at a constant velocity with an arbitrarily set number of rotations to measure the back-electromotive force. The back-electromotive force increases depending on the number of rotations of the rotor 30. It is obvious that the back-electromotive force of the rotor 30 tends to be saturated in change of inclination in combination with the saturation of the field circuit. In this case, an inductance L_0 at no load is considered as a magnetic flux change between 0 [AT] and 0+X [AT]. With regard to the indexes, for example, the inductance at 100 [AT] excitation is described as L_100. The excitation current I indicates (inflow current value of the direct-current power source)×(the number of turns of the field winding 33 on the boss part 321). L_0=(V_x−V_0)/(I_x−I_0)

For example, the inductance at the time of 100 [AT] excitation is expressed as follows: L_100=(V_200−V_100)/(200−100)

In this case, the denominator is already multiplied by the number of turns and thus the permeance value [H] of the rotor 30 equals to these inductance values [H], that is, P=L/N².

Next, a method for calculating the permeance value of the stator 20 will be described with reference to FIGS. 18 and 19. The field winding 33 is caused to generate a magnetic field and excite a field circuit (the d-axis magnetic circuit 36) by a direct-current power source. At this time, while the stator 20 and the rotor 30 are in the foregoing positional relationship, when the stator 20 is energized, a magnetic flux change takes place. When the rotation shaft 31 of the rotary electrical machine is locked to increase the field current If, the magnetomotive force of the stator 20 becomes lower. Accordingly, the decrease in the inductance can be measured. The inductance value is divided by the square of series conductor number of the stator 20 to determine the permeance value, that is, P=L/N².

<About the Relationship Between the Claw-Shaped Magnetic Pole Part Surface Area As and the Boss Part Cross-Sectional Area Ab and the Relationship Between the Boss Part Outer Diameter Db and the Rotor Outer Diameter Dr>

The effective use range of a magnet magnetic flux will be discussed here. In the relational expression described in PTL 1, the condition is partial. Accordingly, when the boss part of the field core is changed in size, the relational expression may not hold. Accordingly, the entire rotor will be taken into account.

In a disc-pole rotary electrical machine, the axial length of the stator can be used completely by generating a magnetic flux at a position (the boss part) not located between the opposing surfaces of the stator and the rotor and passing the magnetic flux in the axial direction. In such a claw-pole rotary electrical machine, as illustrated in FIG. 4, the magnetic flux is output under the condition that the boss part cross-sectional area Ab, the cross-sectional area Ad of the disc part 322 (hereinafter, also called “disc part cross-sectional area Ad”), and root cross-sectional area At of the claw-shaped magnetic pole part 323 (hereinafter, also called “claw-shaped magnetic pole part cross-sectional area At”) are constant in usual.

When a step portion is formed with a decreased cross-sectional area from the boss part 321 to the disc part 322, the decreased cross-sectional area of the portion is regarded as the boss part cross-sectional area Ab or the disc part cross-sectional area Ad. Providing the step portion makes it possible to change the amount of a permissible magnetic flux. Each of the claws (the claw-shaped magnetic pole parts 323) has an opposing surface area (the area of a surface opposing to the appropriate stator 20 corresponding to the boss part cross-sectional area Ab) though which the field flux generated in the boss part 321 can be passed by power distribution to the field winding 33 (not illustrated in FIG. 4) wound on the outer peripheral side of the boss part 321.

As illustrated in FIG. 4, when the disc part 322 extends over the stator 20, the claw-shaped magnetic pole part surface area As can be decreased as compared to the boss part cross-sectional area Ab by the extension of the disc part 322 over the axial length Tst of the stator 20. That is, Ab≈A≈As, or As≈Ab−(Tst−Tb)/2−W can be calculated as an ideal value. In this example, there are increased number of magnetic power sources for the rotor with the permanent magnets 34. Accordingly, another solution should exist.

In the rotor 30 with the permanent magnets 34 and the field circuit, the magnet magnetic flux is branched into two directions, a route passing through the rotor 30 against the field flux (the d-axis magnetic circuit 36) (the second magnet magnetic circuit 39 illustrated in FIG. 10) and a route traveling to the stator 20 (the first magnet magnetic circuit 38 illustrated in FIG. 10). That is, the three cross-sectional areas illustrated in FIG. 4, the boss part cross-sectional area Ab, the disc part cross-sectional area Ad, and the claw-shaped magnetic pole part cross-sectional area At should be smaller than conventional ones. At the same time, the electromotive force needs to be considered while the relationship Ab×B50≥2×Am×Br is satisfied. In addition, at this time, the boss part outer diameter Db (see FIG. 3) becomes small. Accordingly, the arrangement space of the field winding 33 should become larger with decrease in the amount of heat generation.

When the rotor outer diameter Dr (see FIG. 3) is determined, the ratio of the width W of the claw-shaped magnetic pole part 323 to the width of each pole of the boss part 321 hardly changes. Accordingly, the ratio of the rotor outer diameter Dr to the boss part outer diameter Db should be uniquely determined. The boss part outer diameter Db can be calculated from the magnet magnetic flux and the field flux flowing rearward. Needless to say, for suppression of heat generation, the electrical resistance value of the field winding 33 is to be set to 0.1 to 1.0 [Ohm] in a motor or to 1.0 to 3.0 [Ohm] in a power generator, with consideration given to the present air-cooling performance. Ab×B50−2×Am×Bd×(Prt/(Pst+Prt))=Abopt(ideal value of Ab)

In the present technical level, the claw-shaped magnetic pole part surface area As is enough to permit the field flux to flow. The permanent magnets according to the conventional technique mainly play the role of preventing leakage of a magnetic flux between claw-shaped magnetic pole parts. Accordingly, in presently available neodymium magnet-equipped Lundell rotary electrical machines, the claw-shaped magnetic pole part surface areas As are distributed in a range corresponding to the boss part cross-sectional area Ab. That is, the values of As are distributed in a range with reference to Ab satisfying Ab×0.8 to Ab×1.2. In the present disclosure, the calculation formula Bd×(Pst/(Pst+Prt)) can be effectively used. Accordingly, the claw-shaped magnetic pole part surface area As responsible for exchanging the magnetic flux with the stator 20 has a magnet satisfying 2×Am=Ab×B50÷Br in Ab×Bs. Thus, the claw-shaped magnetic pole part surface area As needs to be dimensioned to be sufficient to pass the magnetic flux of the rotor 30 with an optimum value of [As=Bd×Am+Ab×Bs] to the stator 20, which should be larger than Ab×1.2.

The effective use range of the magnet magnetic flux with Ab×B50=2×Am×Br will be discussed. This means that the field circuit needs to be dimensioned to be sufficient to block the magnet magnetic flux. In this state, FIG. 20 indicates the ratio (As/Ab) of the claw-shaped magnetic pole part surface area As to the boss part cross-sectional area Ab on the lateral axis and indicates the interlinked magnetic flux amount under an electrical load on the stator 20 on the vertical axis. As seen from FIG. 20, the interlinked magnetic flux amount usually peaks in an As/Ab range of 1.0 to 1.5, preferably in an As/Ab range of 0.9 to 1.7. The range of As/Ab in the conventional technique (PTL 1) is about 0.4 to 0.8, which does not overlap but diverges from the preferred As/Ab range in the present disclosure.

Further consideration will be given with As/Ab=1.4. The following consideration is based on the assumption that the amount of the field flux and the suppressed amount of the magnet magnetic flux are appropriate and the magnets can be utilized to the same degree as in an IPM rotor. In this case, the optimum value of the boss part outer diameter Db is calculated. FIG. 21 indicates the ratio (Db/Dr) of the boss part outer diameter Db to the rotor outer diameter Dr on the lateral axis and indicates the amount of the interlinked magnetic flux under an electrical load on the stator 20 on the vertical axis. As seen from FIG. 21, the amount of the interlinked magnetic flux peaks around a Db/Dr of 0.51, preferably in a Db/Dr range of 0.46 to 0.53. The Db/Dr range in the conventional technique (PTL 1) is about 0.54 to 0.595, which does not overlap but diverges from the preferred Db/Dr range in the present disclosure.

FIG. 22 indicates the ratio (As/Ab) of the claw-shaped magnetic pole part surface area As to the boss part cross-sectional area Ab on the vertical axis and the ratio (Db/Dr) of the boss part outer diameter Db to the rotor outer diameter Dr on the lateral axis. As seen from FIG. 22, it is obvious that the range in the present disclosure and the range in the conventional technique do not overlap but are separate from each other.

In this consideration, it is assumed that, when the value of Ab×B50=2×Am×Br is large, the magnet has Br=1.2 [T] or so to produce higher effects. The material for the maximum effects is preferably not a Fe magnet with Br=0.4 [T] or so but a neodymium magnet with Br=1 [T] or more. Further, the boss part cross-sectional area Ab is smaller and thus the space saved by the smaller area can be used to decrease the resistance of the field winding 33. This makes it possible to reduce the amount of heat generation by the field winding 33.

<Improvement of Torque>

In a motor (electric motor) using a magnet torque and a reluctance torque, the magnet torque and the reluctance torque are expressed as described below. First, a magnet magnetic flux is designated as Ψ, a q-axis current as Iq, aa d-axis current as Id, a q-axis inductance as Lq, and a d-axis inductance as Ld. In this case, the magnetic torque is expressed as Ψ×Iq. The reluctance torque is expressed as (Lq−Ld)×Id×Iq. Accordingly, a total torque T is expressed as T=Ψ×Iq×(Lq−Ld)×Id×Iq.

In a rotary electrical machine produced in a conventional dimension range and permeance relationship, the saliency ratio ρ (Lq/Ld) of the q-axis inductance Lq to the d-axis inductance Ld is as low as around 1.0. Accordingly, (Lq−Ld) in the torque expression is lower than zero or closer to zero so that sufficient torque cannot be output. However, in the rotary electrical machine produced in the dimension range and permeance relationship of the present disclosure, the saliency ratio ρ can be set to a level at which the relationship Pst:Prt=2n:1 could be attained. Accordingly, it is possible to output a larger torque than conventional ones.

As described above, in the present disclosure, the q-axis inductance Lq is higher than the d-axis inductance Ld. This provides an advantage that the line voltage can be raised. As illustrated in the vector diagrams according to the conventional technique and the technique of the present disclosure of FIGS. 23 and 24, even when the vector sum of the q-axis inductance Lq and the d-axis inductance Ld takes the same inductance value, the vector of voltage V is longer in the case where the q-axis inductance Lq is larger than the d-axis inductance Ld.

That is, in the present disclosure, the voltage is high at low speeds. Accordingly, it is easy to meet the condition “power generation is started when the power generation voltage exceeds the battery voltage”. This provides an advantage that, in the operation of an engine in the situation in which no high-speed rotation is desired such as during idling stop, lower-speed and higher-performance power generation than ever before is possible. When the number of rotations during idling stop is the same as the conventional one, the same voltage can be obtained by the increase of the voltage V even with decrease in the number of turns of the armature winding. This means that the speed at the start of power generation can be decreased or power output at the time of high-speed rotation can be increased in a larger range than ever before.

<About Improvement in Phase Control Performance>

(1) Expressions of Torque, Voltage, and Current

As described above, in a motor (electric motor) with magnet torque and reluctance torque, the magnet torque is expressed as Ψ×Iq and the reluctance torque is expressed as (Lq−Ld)×Id×Iq.

With regard to power generation, the respective generated voltages Vd and Vq of the d and q axes are expressed as Vd=ωLqIq and Vq=ωΨm−ωLdLq with reference to the voltage vector diagram in FIG. 24. According to the expressions of Vd and Vq, as Lq is higher, the voltage is high. This means that the number of rotations at the start of power generation is smaller and the power generation performance under phase control is high.

The power generation current I is expressed as I=(ωΨ−Vbattery)/Z where Z represents impedance and Vbattery represents battery voltage. According to the expression of the power generation current I, as the impedance is lower, the magnet magnetic flux Ψ is large and the power generation current I is high. The present disclosure allows designing in which the magnet magnetic flux is high and the impedance Z (=√R²+2πfL) is low. Accordingly, it is possible to increase the power generation current I as compared to conventional ones.

(2) About the Difference in d Axis Between the Conventional Technique and the Technique of the Present Disclosure

In a usual IPM rotor, the inductance Ld of the d axis is as indicated by a one-dot chain line in FIG. 25. When the d axis is only one as in an IPM rotor, performing phase control for field weakening (performing field weakening by applying an excitation current from the stator to the d axis) allows field weakening control without any waste as in an IPM rotor.

In the present disclosure, however, there are two kinds of d axes, that is, the d axis of the field flux and the d axis of the magnet magnetic flux. In this case, field weakening is performed on the both d axes. Specifically, field weakening is performed on the d axis of the d-axis magnetic circuit 36 illustrated in FIG. 26 and the d axis of the first magnet magnetic circuit 38 illustrated in FIG. 25. At this time, a field weakening magnetic flux (indicated by a dotted line in FIG. 25) weakens the magnetic flux of the d-axis magnetic circuit formed by the field winding of the boss part 321. This operation allows input of a field current to the stator 20 to generate a magnetic flux but also allows input of a field current to the armature winding 25 of the stator 20 to cancel out the generated magnetic flux, which causes a waste of input energy.

In the present disclosure, as described above, the d-axis magnetic circuit 36 is sufficiently saturated to form a magnetic resistance that makes a magnetic flux unlikely to pass. That is, the weakening d-axis magnetic flux from the stator 20 hardly flows into the d-axis magnetic circuit 36. This effectively decreases the d-axis inductance Ld and increases the reluctance torque. The magnetic flux having not flown into the d axis flows toward the q axis. Accordingly, the q-axis inductance Lq increases and the power generation voltages Vd and Vq in the foregoing expression increase. By this action, in the present disclosure, the power generation performance is improved as compared to that in the conventional technique.

<Operations and Advantageous Effects>

In the rotary electrical machine drive system (the rotary electrical machine 2) of the present embodiment, the permanent magnets 34 arranged between the circumferentially adjacent claw-shaped magnetic pole parts 323 form the two magnet magnetic circuits, that is, the first magnet magnetic circuit 38 in which the magnetic flux interlinked with the stator 20 flows and the second magnet magnetic circuit 39 in which the magnetic flux passes through the boss part 321 and returns to the rotor 30. When an electrical load is connected to the rotor 30, that is, when the field current If is distributed by the control device 60 to the field winding 33, the d-axis magnetic circuit 36 is formed in which the magnetic flux formed by the magnetomotive force of the field winding 33 flows through the boss part 321 and the pair of claw-shaped magnetic pole parts 323 of the field core 32, and the stator core 21.

At this time, the flowing direction of the magnet magnetic flux in, of the two magnet magnetic circuits 38 and 39, the second magnet magnetic circuit 39 in which the magnetic flux passes through the boss part 321 and returns to the rotor 30, is opposite to the flowing direction of the magnetic flux in the d-axis magnetic circuit 36. Accordingly, the magnetic flux of the magnet magnetic circuit is unlikely to flow due to the magnetic resistance being large. In the present embodiment, the relationship between the permeance Prt of the d-axis magnetic circuit 36 and the permeance Pst of the q-axis magnetic circuit 37 is set to establish Pst>Prt. This increases the magnet magnetic flux in, of the first and second magnet magnetic circuits 38 and 39, the first magnet magnetic circuit 38. Accordingly, the electric torque generated in the rotor 30 can be significantly improved by the efficient use of the magnet magnetic flux.

The control device 60 in the present disclosure performs phase control such that the rotary electrical machine 1 performs either power running or regeneration. Specifically, when the rotary electrical machine 1 conducts power running (acceleration and speed keeping) or regeneration (simultaneous braking and power generation), the maximum effective torque can be obtained by phase control. In this situation, reluctance torque is generated by applying field-weakening magnetic flux. Applying field-weakening magnetic flux to the d axis means applying the field-weakening magnetic flux to the field core connected to the d axis. That is, at the time of power distribution to the field winding 33, the saturation of the field core 32 is decreased so that the magnetic force of the permanent magnets 34 is not guided to the stator 20 and is not effectively used.

In this case, when the relationship in magnitude between the permeance Prt of the d-axis magnetic circuit 36 and the permeance Pst of the q-axis magnetic circuit 37 is satisfied, the field core 32 is sufficiently saturated. Therefore, the field-weakening magnetic flux is not supplied to the field core 32 so that the reluctance torque can be obtained with little regard to the field-weakening magnetic flux. Accordingly, the performance of power running and regeneration under phase control can be improved in a synergistic manner as compared to the case in which the technique of the present disclosure is applied to operations such as diode rectification and synchronous rectification using only the d axis.

In the present embodiment, the boss part cross-sectional area is designated as Ab and the magnetic flux density of the boss part 321 with a magnetic field of 5000 [A/m] as B50. In addition, the residual magnetic flux density of the permanent magnet 34 is designated as Br and the cross-sectional area of the surface constituting the magnetic pole of the permanent magnet 34 as Am. In the present embodiment, the foregoing elements are set to satisfy the relationship 2×Br [T]×Am [mm²]<B50 [T]×Ab [mm²]. Accordingly, in the present embodiment, the magnetic force generated by the permanent magnet 34 can be absorbed by the d-axis magnetic circuit 36. This makes it possible to decrease the back-electromotive force and suppress the power generated in a high-speed rotation state without power distribution.

In the present embodiment, the ratio of the permeance Prt of the d-axis magnetic circuit 36 to the permeance Pst of the q-axis magnetic circuit 37 is set to Pst:Prt=2n:1 (n is a real number of 1 or larger). Accordingly, the operation mode of the Lundell rotor 30 under an electrical load can be brought closer to that of an IPM rotor. In addition, the saliency ratio ρ as the ratio (Lq/Ld) of the q-axis inductance Lq to the d-axis inductance Ld can be set to 2 or more. Accordingly, in the present embodiment, it is possible to output the same degree of reluctance torque as that in an IPM rotor.

In the present embodiment, the relationship between the claw-shaped magnetic pole part surface area As and the boss part cross-sectional area Ab is set within the range of 0.9<As/Ab<1.7. That is, the claw-shaped magnetic pole part surface area As is larger than the boss part cross-sectional area Ab. Accordingly, in the present embodiment, the permanent magnets 34 that have been conventionally used for the purposes of rectifying a magnetic flux between the adjacent claw-shaped magnetic pole parts 323 and preventing leakage of a magnetic flux, are used like permanent magnets in an IPM rotor. This achieves increase of magnetic flux rather than prevention of leakage of magnetic flux. That is, the permanent magnets can act as a source for torque increase or a source for power increase.

In the present embodiment, the relationship between the boss part outer diameter Db and the rotor outer diameter Dr is set within the range of 0.46<Db/Dr<0.53. In the present embodiment, the boss part cross-sectional area Ab falls within a range determined with maximum consideration given to counteraction of the magnet magnetic force against the magnetic force of the boss part. The magnetic force of the boss part 321 enough to counteract the counteraction of the magnet magnetic force acts on the field core 32. At this time, with the claw-shaped magnetic pole part cross-sectional area At, the total magnetic force of the boss part 321 and the total magnetic force of the magnets can be passed to the stator 20.

In the present embodiment, the residual magnetic flux density Br of the permanent magnet 34 is set to 1 or more [T]. In many cases, the magnetic force of a bond magnet made of neodymium-iron-boron or a plastic-molded magnet formed by injection molding of samarium-iron-nitride is incapable of supplying a sufficient demagnetizing field to the field core 32. That is, the cross-sectional area of the magnet is frequently ensured by reducing the space for the field winding 33. Accordingly, the foregoing operations and advantageous effects can be effectively obtained in particular when the residual magnetic flux density Br of the permanent magnet 34 is 1 or more [T].

In the present embodiment, the portion of the field core 32 with the d-axis magnetic circuit 36 is formed from two kinds of materials different in the saturation flux density Bs. The claw-shaped magnetic pole parts 323 are formed from a material high in the saturation flux density Bs, and the portions other than the claw-shaped magnetic pole parts 323 are formed from a material low in the saturation flux density Bs. Accordingly, in the present embodiment, the boss part 321 becomes quickly saturated in magnetic flux and likely to change to the behavior of magnetic flux characteristics of an IPM rotor. This makes it possible to improve the electric torque in a more reliable manner.

In the present embodiment, the material low in the saturation flux density Bs for the portion other than the claw-shaped magnetic pole parts 323 is higher in magnetic permeability than the material high in the saturation flux density Bs. Accordingly, the effect of absorbing the electromotive force can be enhanced at no load on the rotor 30.

Second Embodiment

A rotary electrical machine drive system according to a second embodiment will be described with reference to FIGS. 29 to 36. A rotary electrical machine 2 in the present embodiment is a vehicle alternating-current power generator as in the first embodiment. The rotary electrical machine drive system according to the present embodiment is different from the first embodiment in having a brushless structure. The different and important points of the present embodiment will be described below. The components in common with the first embodiments will be given the same reference signs and detailed descriptions thereof will be omitted.

<Overall Configuration of the Rotary Electrical Machine Drive System>

A rotary electrical drive system in the present embodiment includes the brushless rotary electrical machine 2 and a control device 60 as illustrated in FIGS. 29 to 31. The rotary electrical machine 2 includes an annular stator 20, a rotor 30, and a housing 10. The stator 20 has an armature winding 25 wound thereon. The rotor 30 is radially opposed to the inner peripheral side of the stator 20. The housing 10 stores the stator 20 and the rotor 30 and a boss part 17 on which the field wire 33 is wound. The control device 60 controls electric current supplied to the field winding 33 and the armature winding 25 to generate electric torque of necessary magnitude in the rotor 30.

The housing 10 includes a hollow cylindrical portion 15, a disc-shaped cover portion 16, and a boss part 17. The cover portion 16 is fitted and fixed to an opening on one end side of the cylindrical portion 15. The boss part 17 protrudes axially from the center of the cover portion 16 and is coaxially arranged on the inner peripheral side of the cylindrical portion 15. A pair of field windings 53 generating a magnetomotive force by energization is wound in a state isolated from the boss part 17. The pair of field windings 53 is connected in parallel and are axially separated from each other. The pair of field windings 53 is connected to the excitation circuit 61 supplying the field current If via an output line 53 a.

The stator 20 has a stator core 21 and an armature winding 25 configured in the same manner as those in the first embodiment. The armature winding 25 is formed from three-phase (U phase, V phase, and W phase) windings U, V, and W (see FIG. 11). Each of the phase windings U, V, and W has one end star-connected to form a neutral point and the other end connected to an output terminal U1, V1, or W1 of the inverter 63.

The rotor 50 is rotatably supported by the boss part 17 via the pair of bearings 14 provided on the both axial ends of the boss part 17 as illustrated in FIG. 29. The rotor 50 is positioned on the radially and axially outside of the pair of field windings 53 and is radially opposed to the inner peripheral side of the stator 20. The rotor 50 is rotationally driven by an engine (not illustrated) installed in the vehicle via a coupling member 47 and a driving force transfer unit (not illustrated) fitted and fixed to a front-side N pole core 52 b. The rotor 50 includes a tandem-type field core 52 and a plurality of permanent magnets 54 as illustrated in FIGS. 32 to 34. The field core 52 has an iron core 52 a, a pair of N pole cores 52 b, an S pole core 52 c, N poles (magnetic pole parts) 52 n, and S poles (magnetic pole parts) 52 s. The permanent magnets 54 are embedded in the iron core 52 a.

The iron core 52 a of the field core 52 is formed in a hollow cylindrical shape as illustrated in FIG. 33. The iron core 52 a has eight N pole holes 52 d circular in cross section, eight S pole holes 52 e circular in cross section, and 16 magnet storage holes 52 f rectangular in cross section. The N poles 52 n are inserted and placed in the N pole holes 52 d. The S poles 52 s are inserted and placed in the S pole holes 52 e. The permanent magnets 54 are embedded in the magnet storage holes 52 f. The eight N pole holes 52 d and the eight S pole holes 52 e are alternately arranged with a predetermined circumferential distance therebetween. The N pole holes 52 d and the S pole holes 52 e are parallel to each other with respect to the central axis line of the iron core 52 a. Accordingly, the N poles 52 n stored in the N pole holes 52 d and the S poles 52 s stored in the S pole holes 52 e are axially extended and are alternately arranged in the circumferential direction on the outer peripheral side of the boss part 17. One magnet storage holes 52 f is provided at a predetermined distance between each the adjacent N pole hole 52 d and S pole hole 52 e.

The pair of N pole cores 52 b is formed in a ring shape as illustrated in FIG. 34. While sandwiching the both axial end surfaces of the iron core 52 a, the inner peripheral surfaces of the N pole cores 52 b are fitted and fixed to the outer peripheral surface of the boss part 17 (see FIG. 29). The N pole cores 52 b has eight each radially recessed concave portions and radially protruding convex portions alternately formed in the circumferential direction at the outer peripheral portions. The convex portions have hold holes 52 g for holding the ends of the N poles 52 n. The both ends of the N poles 52 n are held in the hold holes 52 g of the pair of N pole cores 52 b, with axially central portions inserted and fitted into the N pole holes 52 d of the iron core 52 a.

The S pole core 52 c is formed in a ring shape as illustrated in FIG. 34. The inner diameter of the S pole core 52 c is the same as the inner diameter of the N pole cores 52 b. The S pole core 52 c is positioned between the pair of field windings 53 and is fitted and fixed to the outer peripheral surface of the axial center of the boss part 17 (see FIG. 29). The S pole core 52 c has eight each radially recessed concave portions and radially protruding convex portions alternately formed in the circumferential direction at the outer peripheral portion. The protruding front end surfaces (outer peripheral surfaces) of the convex portions of the S pole core 52 c are at the same positions as the bottom surfaces of the concave portions of the N pole cores 52 b. The S pole core 52 c is arranged such that the protruding front end surfaces of the convex portions are in contact with the inner peripheral surface of the iron core 52 a (see FIG. 29). Accordingly, the S pole core 52 c is magnetically connected to the S poles 52 s stored in the S pole holes 52 e via the iron core 52 a.

In the present embodiment, as in the first embodiment, the outer diameter of the boss part of the field core 52 is designated as Db (hereinafter, also called “boss part outer diameter Db”) and the outer diameter of the rotor 50 (the field core 32) as Dr (hereinafter, also called “rotor outer diameter Dr”). At this time, in the present embodiment, the relationship between the boss part outer diameter Db and the rotor outer diameter Dr is set within the range of 0.46<Db/Dr<0.53. The relationship between the boss part outer diameter Db and the rotor outer diameter Dr will be described later in detail.

As in the first embodiment, the surface area of the outer peripheral surfaces of the N poles 52 n and the S poles 52 s to be magnetic pole parts is designated as As (hereinafter, also called “magnetic pole part surface area As”), and the axially extending iron core cross-sectional area of a pair of NS poles of the boss part as Ab (hereinafter, called “boss part cross-sectional area Ab”). In the present embodiment, the relationship between the magnetic pole part surface area As and the boss part cross-sectional area Ab is set within the range of 0.9<As/Ab<1.7. The boss part cross-sectional area Ab is expressed as A/P where A represents the total cross-sectional area of the cylindrical boss part and P represents the number of pole pairs of the rotary electrical machine.

The permanent magnets 54 have an outer shape with a rectangular cross section and are individually embedded in the magnetic storage holes 52 f of the iron core 52 a. The residual magnetic flux density Br of the permanent magnets 54 is set to 1 or more [T]. The permanent magnets 54 are arranged with an axis of easy magnetization oriented in the circumferential direction. The permanent magnets 54 have magnetic poles formed to match the alternating polarities of the magnetic pole parts (the N poles 52 n and the S poles 52 s) produced by the magnetomotive force of the field windings 53. In the present embodiment, the permanent magnets 54 are arranged in this manner. Accordingly, as illustrated in FIG. 35, each of the permanent magnets 54 has the first and second magnet magnetic circuits 58 and 59.

The first magnet magnetic circuit (indicated by a one-dot chain line in FIG. 35) 58 is a magnetic circuit with, of magnet magnetic fluxes, the magnetic flux passing through the S pole hole 52 e in the iron core 52 a, the permanent magnet 54, and the N pole 52 n and returning to the S pole 52 s in the iron core 52 a through the stator core 21. The second magnet magnetic circuit (indicated by a double line in FIG. 35) 59 is a magnetic circuit with, of the magnet magnetic fluxes, the magnetic flux passing through the S pole 52 s in the iron core 52 a, the permanent magnet 54, and the N pole 52 n, then flowing from the S pole core 52 c through the boss part 17 and the N pole core 52 b and returning to the S pole 52 s in the iron core 52 a, and then returning to in the rotor 50. From the viewpoint of these magnetic fluxes, the second magnet magnetic circuit 59 passing through the boss part 17 is a magnetic circuit with the magnet magnetic flux ineffective for the stator 20, whereas the first magnet magnetic circuit 58 is a magnetic circuit with the magnet magnetic flux interlinked with the stator 20 and forming a back-electromotive force and torque.

The excitation circuit 61 of the control device 60 supplies the field current If from the power source B1 to the field winding 53. The excitation circuit 61 is configured in the same manner as that in the first embodiment and is controlled by the controller (ECU) 67. The inverter 63 supplies the armature current Ia to the armature winding 25 and is configured in the same manner as that in the first embodiment (see FIG. 11). As in the first embodiment, the inverter 63 is controlled by the controller (ECU) 67 based on information from the position sensor 66 that detects the rotation position of the rotor 30.

The field windings 53 generate a magnetomotive force in the boss part 17 by distribution of the field current If from the excitation circuit 61. As a result, the N poles 52 n are N-pole magnetized and the S poles 52 s are S-pole magnetized. Accordingly, as illustrated in FIG. 36, a d-axis magnetic circuit 56 (indicated by a broken line in FIG. 36) is formed such that magnetic flux flows from the boss part 17 of the housing 10 to the pair of N pole cores 52 b and the N pole 52 n, then flows from the S pole 52 s of the iron core 52 a and the S pole core 52 c through the stator core 21, and then returns to the boss part 17. In this case, after passing through the S pole core 52 c in the axially center, the d-axis orientation of the N poles is reversed on the both axial ends, and thus the d-axis magnetic circuit 56 branches the magnetic flux into two directions, d1 and d2, as illustrated in FIG. 29. The d-axis magnetic circuit 56 is a magnetic circuit that generates a back-electromotive force for the rotor 50.

Current flows into the armature winding 25 by the d-axis magnetic circuit 56 and the magnetic flux interlinked with the stator 20 in the first magnet magnetic circuit 58. This forms a q-axis magnetic circuit 57 (indicated by a solid line in FIG. 36). The q-axis magnetic circuit 57 is a magnetic circuit that is formed by the magnetic flux passing through a q axis shifted from the d axis of the stator core 21 at an electrical angle of 90°. In the present embodiment, the relationship between a permeance Prt of the d-axis magnetic circuit 56 and a permeance Pst of the q-axis magnetic circuit 57 are set to establish Pst>Prt under an electrical load on the rotor 50.

In the present embodiment, as in the first embodiment, the ratio of the permeance Prt of the d-axis magnetic circuit 56 to the permeance Pst of the q-axis magnetic circuit 57 are set to Pst:Prt=2n:1 (n is a real number of 1 or larger). Accordingly, the operation mode of the Lundell rotor 50 under an electrical load can be brought closer to that of an IPM rotor. The methods for measuring the permeance Prt of the d-axis magnetic circuit 56 and the permeance Pst of the q-axis magnetic circuit 57 are the same as those in the first embodiment.

In the present embodiment, the d-axis magnetic circuit 56 and the first magnet magnetic circuit 58 share the magnetic circuit from the S pole 52 s, through the iron core 52 a, the stator 20, and the iron core 52 a to the N pole 52 n. In addition, the d-axis magnetic circuit 56 and the second magnet magnetic circuit 59 share part of the magnetic circuit flowing from the S pole 52 s of the rotor 50 through the iron core 52 a, the S pole core 52 c, the boss part 17, and the N pole cores 52 b, and returning to the N pole 52 n. Accordingly, the d-axis magnetic circuit 56 and at least parts of the first and second magnet magnetic circuits 58 and 59 are shared.

In the present embodiment, as in the first embodiment, the axially extending iron core cross-sectional area of a pair of NS poles of the boss part 17 is designated as Ab and the magnetic flux density of the boss part 17 with a magnetic field of 5000 [A/m] as B50. In addition, the residual magnetic flux density of the permanent magnet 54 arranged between the N pole 52 n and the S pole 52 s is designated as Br and the cross-sectional area of the plane constituting the magnetic pole of the permanent magnet 54 as Am. In the present embodiment, the foregoing elements are set to establish the relationship 2×Br [T]×Am [mm²]<B50 [T]×Ab [mm²].

The portions of the field core 52 and the housing 10 with the d-axis magnetic circuit 56 are formed from two kinds of materials different in the saturation flux density Bs. In the present embodiment, the N poles 52 n and the S poles 52 s as magnetic pole parts are formed from a material high in the saturation flux density Bs, and the portions other than the N poles 52 n and the S poles 52 s are formed from a material low in the saturation flux density Bs. Examples of a material high in the saturation flux density Bs and a material low in the saturation flux density Bs are the same as those in the first embodiment.

<Operations and Advantageous Effects>

In the rotary electrical machine drive system (the rotary electrical machine 2) of the present embodiment, when an electrical load is connected to the rotor 50, the relationship between the permeance Prt of the d-axis magnetic circuit 56 and the permeance Pst of the q-axis magnetic circuit 57 are set to establish the relationship Pst>Prt. Accordingly, as in the first embodiment, the magnet magnetic flux increases in the first magnet magnetic circuit 58 formed by the magnetic flux interlinked with the stator 20 and flowing in the same direction as that in the d-axis magnetic circuit 56. In the present embodiment, the electric torque can be significantly improved by the efficient use of the magnet magnetic flux.

In particular, the brushless rotary electrical machine is not subjected to current limitation due to a brush. Accordingly, it is possible to increase the value of the field current If that would be restricted due to a brush. This makes it possible to saturate the field circuit (the d-axis magnetic circuit 56) and use efficiently the magnet force even in the brushless rotary electrical machine 2. Accordingly, with regard to centrifugal force as a weak point of the magnet-equipped Lundell rotor, the rear side of the magnetic pole parts is not subjected to the centrifugal force of the electrical circuit. This makes it possible to decrease stress resulting from centrifugal force.

The control device 60 in the present embodiment performs phase control such that the rotary electrical machine 2 performs either power running or regeneration. Accordingly, in the present embodiment, the relationship in magnitude between the permeance Prt of the d-axis magnetic circuit 36 and the permeance Pst of the q-axis magnetic circuit 37 is satisfied. This makes it possible to improve the performance of power running and regeneration under phase control in a synergistic manner as compared to the case in which the technique of the present disclosure is applied to operations such as diode rectification and synchronous rectification using only the d axis.

In the present embodiment, the boss part cross-sectional area is designated as Ab and the magnetic flux density of the boss part 17 with a magnetic field of 5000 [A/m] as B50. In addition, the residual magnetic flux density of the permanent magnet 54 is designated as Br and the cross-sectional area of the surface of the permanent magnet 54 constituting the magnetic pole as Am. In the present embodiment, the foregoing elements are set to establish the relationship 2×Br [T]×Am [mm²]<B50 [T]×Ab [mm²]. Accordingly, in the present embodiment, as in the first embodiment, it is possible to decrease the back-electromotive force and suppress the power generated in a high-speed rotation state without power distribution.

In the present embodiment, the ratio of the permeance Prt of the d-axis magnetic circuit 56 to the permeance Pst of the q-axis magnetic circuit 57 is set to Pst:Prt=2n:1 (n is a real number of 1 or larger). Accordingly, in the present embodiment, as in the first embodiment, the saliency ratio ρ can be set to 2 or more to output the same degree of reluctance torque as that in an IPM rotor.

In the present embodiment, the relationship between the magnetic pole part surface area As and the boss part cross-sectional area Ab is set within the range of 0.9<As/Ab<1.7. That is, the magnetic pole part surface area As is larger than the boss part cross-sectional area Ab. Accordingly, in the present embodiment, the permanent magnets 54 that have been conventionally used for the purposes of rectifying a magnetic flux between the adjacent magnetic pole parts and preventing leakage of a magnetic flux, are used like permanent magnets in an IPM rotor. This achieves increase of magnetic flux rather than prevention of leakage of magnetic flux. That is, the permanent magnets can act as a source for torque increase or a source for power increase.

In the present embodiment, the relationship between the boss part outer diameter Db and the rotor outer diameter Dr is set within the range of 0.46<Db/Dr<0.53. In the present embodiment, the boss part cross-sectional area Ab falls within a range determined in maximum consideration given to counteraction of the magnet magnetic force against the magnetic force of the boss part. The magnetic force of the boss part enough to counteract the counteraction of the magnet magnetic force acts on the field core 52. At this time, with the root cross-sectional area At of the N poles 52 n and the S poles 52 s as magnetic pole parts, the total magnetic force of the boss part and the total magnetic force of the magnets can be passed to the stator 20.

In the present embodiment, the residual magnetic flux density Br of the permanent magnet 54 is set to 1 or more [T]. In many cases, the magnetic force of a bond magnet made of neodymium-iron-boron or a plastic-molded magnet formed by injection molding of samarium-iron-nitride is incapable of supplying a sufficient demagnetizing field to the field core 52. That is, the cross-sectional area of the magnet is frequently ensured by reducing the space for the field windings 53. Accordingly, the foregoing operations and advantageous effects can be effectively obtained in particular when the residual magnetic flux density Br of the permanent magnet 54 is 1 or more [T].

In the present embodiment, the field core 51 with the d-axis magnetic circuit 56 caused by magnetomotive force of the field windings 55 is formed from two kinds of materials different in the saturation flux density Bs. The N poles 52 n and the S poles 52 s are formed from a material high in the saturation flux density Bs, and the portions other than the N poles 52 n and the S poles 52 s are formed from a material low in the saturation flux density Bs. Accordingly, in the present embodiment, the boss part 321 becomes quickly saturated in magnetic flux and likely to change to the behavior of magnetic flux characteristics of an IPM rotor. This makes it possible to improve the electric torque in a more reliable manner.

In the present embodiment, the material low in the saturation flux density Bs for the portion other than the N poles 52 n and the S poles 52 s is higher in magnetic permeability than the material high in the saturation flux density Bs. Accordingly, the effect of absorbing the electromotive force can be enhanced at no load on the rotor 30.

Third Embodiment

A rotary electrical machine drive system according to a third embodiment will be described with reference to FIG. 37. The rotary electrical machine drive system according to the present embodiment is a vehicle alternating-current power generator as in the first embodiment. The rotary electrical machine according to the present embodiment is different from the first embodiment in the structure of the pole cores constituting the field core. The different and important points of the present embodiment will be described below. The components in common with the first embodiment will be given the same reference signs and detailed descriptions thereof will be omitted.

<Configuration of the Field Core>

The field core 32 includes the first pole core 32 a and the second pole core 32 b. As illustrated in FIG. 37, the first pole core 32 a includes the first boss part 321 a, the first disc part 322 a, and the first claw-shaped magnetic pole parts 323 a. The first disc part 322 a has a groove portion 322 c to decrease the area of the cross section orthogonal to the flowing direction of the magnetic flux. The groove portion 322 c is formed on the inner surface of the first disc part 322 a axially opposed to the second disc part 322 b. The groove portion 322 c is formed to circumferentially extend in an arc shape from a portion connected to the outermost first claw-shaped magnetic pole parts 323 a as seen in the radial direction of the first disc part 322 a.

The magnetic flux flows axially in the first disc part 322 a. The arc-shaped groove portion 322 c is formed on the inner surface of the first disc part 322 a axially opposed to the second disc part 322 b to circumferentially extend from the position connected to the outermost first claw-shaped magnetic pole parts 323 a as seen in the radial direction. Accordingly, due to the groove portion 322 c, the area of the cross section orthogonal to the flowing direction of the magnetic flux is decreased. That is, the cross section of the outermost periphery of the first disc part 322 a connected to the first claw-shaped magnetic pole parts 323 a becomes small.

In the present embodiment, the relationship between the area A1 of the circle with a diameter equivalent to the outer diameter Dr of the first pole core 32 a as the outer diameter of the rotor 30 and the cross-sectional area A2 of the portion with the minimum area of the cross section orthogonal to the flowing direction of the magnetic flux is set within a range of 0.2116<A2/A1<0.2809. The cross-sectional area A2 is obtained by multiplying a cross-sectional area A0 of a portion of the first disc part 322 a with the groove portion 322 connected to the first claw-shaped magnetic pole parts 323 a by the number of pole pairs P.

The second pole core 32 b is identical in shape to the first pole core 32 a. Accordingly, the second disc part 322 b has a groove portion to decrease the area of the cross section orthogonal to the flowing direction of the magnetic flux.

<Operations and Advantageous Effects>

In the rotary electrical machine drive system of the present embodiment, the field core 32 has the decreased area of the cross section orthogonal to the flowing direction of the magnetic flux. Specifically, the cross-sectional area of the disc part is decreased. This changes the characteristics of the vehicle alternating-current power generator. That is, it is easy to form vehicle alternating-current power generators different in characteristics. Further, in the present embodiment, the relationship between the area A1 of the circle with a diameter equivalent to the outer diameter Dr of the rotor and the cross-sectional area A2 of the portion with the minimum area of the cross section orthogonal to the flowing direction of the magnetic flux is set within the range of 0.2116<A2/A1<0.2809. This makes it possible to ensure the same magnetic relationship and produce the same advantageous effects as those in the case of setting the relationship between the outer diameter Db of the boss part and the outer diameter Dr of the rotor in the range of 0.46<Db/Dr<0.53.

In the present embodiment, the arc-shaped groove portions are formed at the first boss part 322 a and the second boss part 322 b. This decreases the area of the cross section orthogonal to the flowing direction of the magnetic flux. The arc-shaped groove portions can be easily processed by a milling machine or the like. Accordingly, the area of the cross section orthogonal to the flowing direction can be easily decreased. In addition, the arc-shaped groove portions are formed only on the inner surfaces of the first disc part 322 a and the second disc part 322 b, which makes it possible to use continuously the field windings, the winding frames, and other components that have been used before the formation of the groove portions. Accordingly, in the present embodiment, in the case of forming vehicle alternating-current power generators different in characteristics, the costs resulting from the change of characteristics can be suppressed.

Fourth Embodiment

A rotary electrical machine drive system according to a fourth embodiment will be described with reference to FIG. 38. The rotary electrical machine according to the present embodiment is a vehicle alternating-current power generator as in the first embodiment. The rotary electrical machine according to the present embodiment is different from the first embodiment in the structure of the pole cores constituting the field core. The rotary electrical machine according to the present embodiment has the decreased cross-sectional area of the disc part. In the rotary electrical machine according to the present embodiment, the cross section of part of the disc part is decreased in a configuration different from that of the third embodiment. The different and important points of the present embodiment will be described below. The components in common with the first embodiment will be given the same reference signs and detailed descriptions thereof will be omitted.

<Configuration of the Field Core>

The field core 32 includes the first pole core 32 a and the second pole core 32 b. As illustrated in FIG. 38, the first pole core 32 a includes the first boss part 321 a, the first disc part 322 a, and the first claw-shaped magnetic pole parts 323 a. The first disc part 322 a has groove portions 322 d and 322 e of different widths to decrease the area of the cross section orthogonal to the flowing direction of the magnetic flux. The groove portions 322 d and 322 e are formed on the inner surface of the first disc part 322 a axially orthogonal to the second disc part 322 b. The groove portions 322 d and 322 e are formed to extend in a radial pattern outward as seen in the radial direction from predetermined positions radially inside the first disc part 322 a.

The magnetic flux flows radially in the first disc part 322 a. The first disc part 322 a has the groove portions 322 d and 322 e formed to extend in a radial pattern outward as seen in the radial direction from a predetermined position radially inside the first disc part 322 a. Accordingly, due to the groove portions 322 d and 322 e, the area of the cross section orthogonal to the flowing direction of the magnetic flux is decreased. That is, the cross section of the outermost periphery of the first disc part 322 a connected to the first claw-shaped magnetic pole parts 323 a becomes small.

In the present embodiment, as in the third embodiment, the relationship between the area A1 of the circle with a diameter equivalent to the outer diameter Dr of the first pole core 32 a as the outer diameter of the rotor 30 and the cross-sectional area A2 of the portion with the minimum area of the cross section orthogonal to the flowing direction of the magnetic flux is set within the range of 0.2116<A2/A1<0.2809. As in the third embodiment, the cross-sectional area A2 is obtained by multiplying the cross-sectional area A1 of the first disc part 322 a connected to the first claw-shaped magnetic pole parts 323 a by the number of pole pairs P.

The second pole core 32 b is identical in shape to the first pole core 32 a. Accordingly, the second disc part 322 b has a groove portion to decrease the area of the cross section orthogonal to the flowing direction of the magnetic flux.

<Operations and Advantageous Effects>

In the rotary electrical machine drive system of the present embodiment, the field core 32 has the decreased area of the cross section orthogonal to the flowing direction of the magnetic flux. Specifically, the cross-sectional area of the disc part is decreased. This changes the characteristics of the vehicle alternating-current power generator. That is, it is easy to form vehicle alternating-current power generators different in characteristics. Further, in the present embodiment, the relationship between the area A1 of the circle with a diameter equivalent to the outer diameter Dr of the rotor and the cross-sectional area A2 of the portion with the minimum area of the cross section orthogonal to the flowing direction of the magnetic flux is set within the range of 0.2116<A2/A1<0.2809. Accordingly, in the present embodiment, it is possible to ensure the same magnetic relationship and produce the same advantageous effects as those in the case of setting the relationship between the outer diameter Db of the boss part and the outer diameter Dr of the rotor in the range of 0.46<Db/Dr<0.53.

In the present embodiment, the groove portions are formed to extend radially in a radial pattern at the first disc part 322 a and the second disc part 322 b. As a result, a rib with high second moment of area is radially formed in a radial pattern between the groove portions. Accordingly, in the present embodiment, it is possible to improve the rigidity of the field core 32 against centrifugal force as compared to the third embodiment. In addition, the formation of the groove portions decreases the contact area between the first disc part 322 a and the field winding 33 and the contact area between the second disc part 322 b and the field winding 33. Accordingly, in the present embodiment, even when the field core 32 generates heat due to eddy current, the heat transfer from the field core 32 to the field winding 33 can be suppressed. Therefore, it is possible to suppress heat deterioration and improve the reliability of the field winding 33. In the present embodiment, as in the third embodiment, it is possible to use continuously the field winding, the winding frame, and other components that have been used before the formation of the groove portions. Accordingly, in the case of forming vehicle alternating-current power generators different in characteristics, the costs resulting from the change of characteristics can be suppressed.

Fifth Embodiment

A rotary electrical machine drive system according to a fifth embodiment will be described with reference to FIG. 39. The rotary electrical machine according to the present embodiment is a vehicle alternating-current power generator as in the first embodiment. The rotary electrical machine according to the present embodiment is different from the first embodiment in the structure of the pole cores constituting the field core. In the rotary electrical machine according to the present embodiment, the cross section of part of the boss part is decreased unlike in the third and fourth embodiments. The different and important points of the present embodiment will be described below. The components in common with the first embodiment will be given the same reference signs and detailed descriptions thereof will be omitted.

<Configuration of the Field Core>

The field core 32 includes the first pole core 32 a and the second pole core 32 b. As illustrated in FIG. 39, the first pole core 32 a includes the first boss part 321 a, the first disc part 322 a, and the first claw-shaped magnetic pole parts 323 a. The first boss part 321 a has a groove portion 321 c to decrease the area of the cross section orthogonal to the flowing direction of the magnetic flux. The groove portion 321 c is formed in a circular shape on the outer peripheral surface of an axially intermediate portion of the first boss part 321 a.

The magnetic flux flows axially in the first boss part 321 a. The first boss part 321 a has the circular groove portion 321 c on the outer peripheral surface of the axially intermediate portion. Accordingly, due to the groove portion 321 c, the area of the cross section orthogonal to the flowing direction of the magnetic flux is decreased. That is, the cross section of the axially intermediate portion of the first boss part 321 a becomes smaller than the other portions.

In the present embodiment, the relationship between the area A1 of the circle with a diameter equivalent to the outer diameter Dr of the first pole core 32 a as the outer diameter of the rotor 30 and the cross-sectional area A2 of the portion with the minimum area of the cross section orthogonal to the flowing direction of the magnetic flux is set within the range of 0.2116<A2/A1<0.2809. The cross-sectional area A2 is the cross-sectional area of a portion of the first boss part 321 a having the groove portion 321 c and is the area of the cross section of the portion having the groove portion 321 c orthogonal to the axial direction.

The second pole core 32 b is identical in shape to the first pole core 32 a. Accordingly, the second boss part 321 b has a groove portion to decrease the area of the cross section orthogonal to the flowing direction of the magnetic flux.

<Operations and Advantageous Effects>

In the rotary electrical machine drive system of the present embodiment, the field core 32 has the decreased area of the cross section orthogonal to the flowing direction of the magnetic flux. Specifically, the cross-sectional area of the boss part is decreased. This changes the characteristics of the vehicle alternating-current power generator. That is, it is easy to form vehicle alternating-current power generators different in characteristics. Further, in the present embodiment, the relationship between the area A1 of the circle with a diameter equivalent to the outer diameter Dr of the rotor and the cross-sectional area A2 of the portion with the minimum area of the cross section orthogonal to the flowing direction of the magnetic flux is set within the range of 0.2116<A2/A1<0.2809. Accordingly, in the present embodiment, it is possible to ensure the same magnetic relationship and produce the same advantageous effects as those in the case of setting the relationship between the outer diameter Db of the boss part and the outer diameter Dr of the rotor in the range of 0.46<Db/Dr<0.53.

In the present embodiment, the groove portions are formed at the first boss part 321 a and the second boss part 321 b. Accordingly, the field core 32 can be formed without reducing rigidity against centrifugal force. In the present embodiment, as in the third embodiment, it is possible to use continuously the field winding, the winding frame, and other components that have been used before the formation of the groove portions. Accordingly, in the case of forming vehicle alternating-current power generators different in characteristics, the costs resulting from the change of characteristics can be suppressed.

Sixth Embodiment

A rotary electrical machine drive system according to a sixth embodiment will be described with reference to FIG. 40. The rotary electrical machine according to the present embodiment is a vehicle alternating-current power generator as in the first embodiment. The rotary electrical machine according to the present embodiment is different from the first embodiment in the structure of the pole cores constituting the field core. In the rotary electrical machine according to the present embodiment, as in the fifth embodiment, the cross section of the boss part is decreased. In the rotary electrical machine according to the present embodiment, the cross section of part of the boss part is decreased at a position different from that in the fifth embodiment. The different and important points of the present embodiment will be described below. The components in common with the first embodiment will be given the same reference signs and detailed descriptions thereof will be omitted.

<Configuration of the Field Core>

The field core 32 includes the first pole core 32 a and the second pole core 32 b. As illustrated in FIG. 40, the first pole core 32 a includes the first boss part 321 a, the first disc part 322 a, and the first claw-shaped magnetic pole part 323 a. The first boss part 321 a has a small-diameter portion 321 d to decrease the area of the cross section orthogonal to the flowing direction of the magnetic flux. The small-diameter portion 321 d is smaller in outer diameter than the other portions and is formed at an axial end of the first boss part 321 a axially opposed to the second boss part 321 b.

The magnetic flux axially flows in the first boss part 321 a. The small-diameter portion 321 d smaller in outer diameter than the other portions is formed at the axial end of the first boss part 321 a. Accordingly, due to the small-diameter portion 321 d, the area of the cross section orthogonal to the flowing direction of the magnetic flux becomes small. That is, the cross section of the axial end of the first boss part 321 a becomes smaller than the other portions.

In the present embodiment, the relationship between the area A1 of the circle with a diameter equivalent to the outer diameter Dr of the first pole core 32 a as the outer diameter of the rotor 30 and the cross-sectional area A2 of the portion with the minimum area of the cross section orthogonal to the flowing direction of the magnetic flux is set within the range of 0.2116<A2/A1<0.2809. The cross-sectional area A2 is the cross-sectional area of a portion of the first boss part 321 a having the small-diameter portion 321 d and is the area of the cross section of the portion having the small-diameter portion 321 d orthogonal to the axial direction.

The second pole core 32 b is identical in shape to the first pole core 32 a. Accordingly, the second boss part 321 b has a small-diameter portion to decrease the area of the cross section orthogonal to the flowing direction of the magnetic flux.

<Operations and Advantageous Effects>

The rotary electrical machine drive system in the present embodiment can produce the same advantageous effects as those of the fifth embodiment.

Seventh Embodiment

A rotary electrical machine drive system according to a seventh embodiment will be described with reference to FIG. 41. The rotary electrical machine according to the present embodiment is a vehicle alternating-current power generator as in the first embodiment. The rotary electrical machine according to the present embodiment is different from the first embodiment in the structure of the pole cores constituting the field core. In the rotary electrical machine according to the present embodiment, the cross-sectional area of the boss part is decreased. In the rotary electrical machine according to the present embodiment, the cross section of part of the boss part is decreased in a configuration different from those of the fifth and sixth embodiments. The different and important points of the present embodiment will be described below. The components in common with the first embodiment will be given the same reference signs and detailed descriptions thereof will be omitted.

<Configuration of the Field Core>

The field core 32 includes the first pole core 32 a and the second pole core 32 b. As illustrated in FIG. 41, the first pole core 32 a includes the first boss part 321 a, the first disc part 322 a, and the first claw-shaped magnetic pole parts 323 a. The first boss part 321 a has a chamfered portion 321 e to decrease the area of the cross section orthogonal to the flowing direction of the magnetic flux. The first boss part 321 a has a through hole portion 321 f to fit with the rotation shaft 31. The chamfered portion 321 e is formed on the entire periphery of the axial end of the through hole portion 321 f on the first disc part 322 a side.

The magnetic flux flows axially in the first boss part 321 a. The magnetic flux also flows radially in the first disc part 322 a. The flow of the magnetic flux changes from the axial direction to the radial direction or from the radial direction to the axial direction in the portion of the first boss part 321 a on the first disc part 322 a side connected to the first disc part 322 a. The chamfered portion 321 e is formed on the entire periphery of the axial end of the through hole portion 321 f on the first disc part 322 a side. Accordingly, due to the chamfered portion 321 e, the area of the cross section orthogonal to the flowing direction of the magnetic flux is decreased.

In the present embodiment, the relationship between the area A1 of the circle with a diameter equivalent to the outer diameter Dr of the first pole core 32 a as the outer diameter of the rotor 30 and the cross-sectional area A2 of the portion with the minimum area of the cross section orthogonal to the flowing direction of the magnetic flux is set within the range of 0.2116<A2/A1<0.2809. In this example, the point at which the outer peripheral surface of the first boss part 321 a is in contact with the inner surface of the first disc part 322 a is designated as K, and the line connecting the point K with an inclination surface 321 g of the chamfered portion 321 e at the minimum distance as M. The cross-sectional area A2 is the area of a cross section cut along the line M.

The second pole core 32 b is identical in shape to the first pole core 32 a. Accordingly, the second boss part 321 b has a chamfered portion to decrease the area of the cross section orthogonal to the flowing direction of the magnetic flux.

<Operations and Advantageous Effects>

In the rotary electrical machine drive system of the present embodiment, the field core 32 has the decreased area of the cross section orthogonal to the flowing direction of the magnetic flux. Specifically, the cross-sectional area of the boss part is decreased. This changes the characteristics of the vehicle alternating-current power generator. That is, it is easy to form vehicle alternating-current power generators different in characteristics. Further, in the present embodiment, the relationship between the area A1 of the circle with a diameter equivalent to the outer diameter Dr of the rotor and the cross-sectional area A2 of the portion with the minimum area of the cross section orthogonal to the flowing direction of the magnetic flux is set within the range of 0.2116<A2/A1<0.2809. Accordingly, in the present embodiment, it is possible to ensure the same magnetic relationship and produce the same advantageous effects as those in the case of setting the relationship between the outer diameter Db of the boss part and the outer diameter Dr of the rotor in the range of 0.46<Db/Dr<0.53.

In the present embodiment, the chamfered portions are formed at the first boss part 321 a and the second boss part 321 b. Accordingly, the area of the cross section orthogonal to the flowing direction of the magnetic flux is decreased. The chamfered portions can be easily processed by drilling or the like. Accordingly, it is easy to decrease the area of the cross section orthogonal to the flowing direction. In addition, the chamfered portions are formed only at the axial ends of the through holes in the first boss part 321 a and the second boss part 321 b, which makes it possible to use continuously the field winding, the winding frame, and other components that have been used before the formation of the chamfered portions. Accordingly, in the present embodiment, in the case of forming vehicle alternating-current power generators different in characteristics, the costs resulting from the change of characteristics can be suppressed.

Eighth Embodiment

A rotary electrical machine system according to an eighth embodiment will be described with reference to FIG. 42. The rotary electrical machine according to the present embodiment is a vehicle alternating-current power generator as in the first embodiment. The rotary electrical machine according to the present embodiment is different from the first embodiment in the structure of the pole cores constituting the field core. The rotary electrical machine according to the present embodiment has the decreased cross-sectional area of the boss part. In the rotary electrical machine according to the present embodiment, the cross section of part of the boss part is decreased at a position different from that in the seventh embodiment. The different and important points of the present embodiment will be described below. The components in common with the first embodiment will be given the same reference signs and detailed descriptions thereof will be omitted.

<Configuration of the Field Core>

The field core 32 includes the first pole core 32 a and the second pole core 32 b. As illustrated in FIG. 42, the first pole core 32 a includes the first boss part 321 a, the first disc part 322 a, and the first claw-shaped magnetic pole parts 323 a. The first boss part 321 a has a chamfered portion 321 h to decrease the area of the cross section orthogonal to the flowing direction of the magnetic flux. The chamfered portion 321 h is formed on the entire periphery of the axial end of the through hole portion 321 f on the second boss part 321 b side.

The magnetic flux flows axially in the first boss part 321 a. The chamfered portion 321 h is formed at the axial end of the through hole portion 321 f on the second boss part 321 b side. Accordingly, due to the chamfered portion 321 h, the area of the cross section orthogonal to the flowing direction of the magnetic flux is decreased. That is, the cross section of the axial end of the first boss part 321 a becomes smaller than the other portions.

<Operations and Advantageous Effects>

The rotary electrical machine drive system in the present embodiment can produce the same advantageous effects as those of the seventh embodiment.

Ninth Embodiment

A rotary electrical machine drive system according to a ninth embodiment will be described with reference to FIG. 43. The rotary electrical machine according to the present embodiment is a vehicle alternating-current power generator as in the first embodiment. The rotary electrical machine according to the present embodiment is different from the first embodiment in the structure of the pole cores constituting the field core. The rotary electrical machine according to the present embodiment has the decreased cross-sectional area of the boss part. In the rotary electrical machine according to the present embodiment, the cross section of part of the boss part is decreased in a configuration different from those in the fifth to eighth embodiments. The different and important points of the present embodiment will be described below. The components in common with the first embodiment will be given the same reference signs and detailed descriptions thereof will be omitted.

<Configuration of the Field Core>

The field core 32 includes the first pole core 32 a and the second pole core 32 b. As illustrated in FIG. 43, the first pole core 32 a includes the first boss part 321 a, the first disc part 322 a, and the first claw-shaped magnetic pole parts 323 a. The first boss part 321 a has a groove portion 321 i to decrease the area of the cross section orthogonal to the flowing direction of the magnetic flux. The groove portion 321 i is formed on the axial end surface of the first boss part 321 a axially opposed to the second boss part 321 b.

The magnetic flux flows axially in the first boss part 321 a. The circular groove portion 321 i is formed at the axial end surface of the first boss part 321 a. Accordingly, due to the groove portion 321 i, the area of the cross section orthogonal to the flowing direction of the magnetic flux is decreased. That is, the cross section of the axial end of the first boss part 321 a becomes smaller than the other portions.

In the present embodiment, the relationship between the area A1 of the circle with a diameter equivalent to the outer diameter Dr of the first pole core 32 a as the outer diameter of the rotor 30 and the cross-sectional area A2 of the portion with the minimum area of the cross section orthogonal to the flowing direction of the magnetic flux is set within the range of 0.2116<A2/A1<0.2809. In this example, the cross-sectional area A2 is the cross-sectional area of the axial end of the first boss part 321 a having the groove portion 321 i. The cross-sectional area A2 is the sum of the areas of the axial end surfaces of cylindrical portions 321 j and 321 k formed by providing the groove portion 321 i.

The second pole core 32 b is identical in shape to the first pole core 32 a. The second boss part 321 b has a groove portion to decrease the area of the cross section orthogonal to the flowing direction of the magnetic flux.

<Operations and Advantageous Effects>

The rotary electrical machine drive system in the present embodiment can produce the same advantageous effects as those of the fifth embodiment.

Tenth Embodiment

A rotary electrical machine drive system according to a tenth embodiment will be described with reference to FIG. 44. The rotary electrical machine according to the present embodiment is a vehicle alternating-current power generator as in the first embodiment. The rotary electrical machine according to the present embodiment is different from the first embodiment in the structure of the pole cores constituting the field core. The rotary electrical machine according to the present embodiment is equivalent to a modified mode of the ninth embodiment. The different and important points of the present embodiment will be described below. The components in common with the first embodiment will be given the same reference signs and detailed descriptions thereof will be omitted.

<Configuration of the Field Core>

As illustrated in FIG. 44, the first boss part 321 a has groove portions 321 l and 321 m to decrease the area of the cross section orthogonal to the flowing direction of the magnetic flux. The groove portions 321 l and 321 m are concentrically formed at the axial end surface of the first boss part 321 a axially opposed to the second boss part 321 b. Accordingly, due to the groove portions 321 l and 321 m, the area of the cross section orthogonal to the flowing direction of the magnetic flux is decreased. That is, the cross section of the axial end of the first boss part 321 a becomes smaller than the other portions.

In the present embodiment, the relationship between the area A1 of the circle with a diameter equivalent to the outer diameter Dr of the first pole core 32 a as the outer diameter of the rotor 30 and the cross-sectional area A2 of the portion with the minimum area of the cross section orthogonal to the flowing direction of the magnetic flux is set within the range of 0.2116<A2/A1<0.2809. The cross-sectional area A2 is the cross-sectional area of the axial end of the first boss part 321 a with the groove portions 321 l and 321 m. The cross-sectional area A2 is the sum of the areas of the axial end surfaces of cylindrical portions 321 n to 321 p formed by providing the groove portions 321 l and 321 m.

<Operations and Advantageous Effects>

The rotary electrical machine drive system in the present embodiment can produce the same advantageous effects as those of the fifth embodiment.

Eleventh Embodiment

A rotary electrical machine drive system according to an eleventh embodiment will be described with reference to FIG. 45. The rotary electrical machine according to the present embodiment is a vehicle alternating-current power generator as in the second embodiment. The rotary electrical machine according to the present embodiment is different from the second embodiment in the structure of the pole cores constituting the field core. In the rotary electrical machine according to the present embodiment, the field core in the third embodiment is changed to a brushless structure. The different and important points of the present embodiment will be described below. The components in common with the second embodiment will be given the same reference signs and detailed descriptions thereof will be omitted. The constituent elements corresponding to those of the field core in the third embodiment will be given the same designations as those of the field core in the third embodiment.

<Configuration of the Field Core>

As illustrated in FIG. 45, the field core 52 includes a first pole core 52 h and a second pole core 52 i.

The first pole core 52 h includes a first disc part 522 h and first claw-shaped magnetic pole parts 523 h. The first pole core 52 h is structured such that the first boss part 321 a is removed from the first pole core 32 a in the third embodiment. The first disc part 522 h has a groove portion 522 j to decrease the area of the cross section orthogonal to the flowing direction of the magnetic flux. The groove portion 522 j is formed on the inner surface of the first disc part 522 h axially opposed to the second disc part 522 i. The groove portion 522 j is circumferentially extended in an arc shape from a portion connected to the outermost first claw-shaped magnetic pole parts 523 h as seen in the radial direction of the first disc part 522 h.

The second pole core 52 i includes a second boss part 521 i, a second disc part 522 i, and second claw-shaped magnetic pole parts 523 i. The second pole core 52 i is identical in configuration to the first pole core 32 a in the third embodiment. The second disc part 522 i has a groove portion 522 k to decrease the area of the cross section orthogonal to the flowing direction of the magnetic flux. The groove portion 522 k is formed on the inner surface of the second disc part 522 i axially opposed to the first disc part 522 h. The groove portion 522 k is circumferentially extended in an arc shape from a portion connected to the outermost second claw-shaped magnetic pole parts 523 i as seen in the radial direction of the second disc part 522 i.

The first pole core 52 h is arranged such that the inner peripheral surface of the first disc part 522 h is radially opposed to the outer peripheral surface of the boss part 17 with a space therebetween. The second pole core 52 i has the first claw-shaped magnetic pole parts 523 h and the second claw-shaped magnetic pole parts 523 i alternately arranged in the circumferential direction. The second pole core 52 i is arranged such that the axial end surface of the second boss part 521 i is axially opposed to the axial end surface of the boss part 17 with a space therebetween. The permanent magnets 54 are arranged between the circumferentially adjacent first claw-shaped magnetic pole parts 523 h and second claw-shaped magnetic pole parts 523 i. The permanent magnets 54 are arranged with an axis of easy magnetization oriented in the circumferential direction. The permanent magnets 54 have magnetic poles formed to match the alternating polarities of the first claw-shaped magnetic pole parts 523 h and the second claw-shaped magnetic pole parts 523 i by the magnetomotive force of the field windings 53. In the first pole core 52 h and the second pole core 52 i, the inner peripheral sides of the first claw-shaped magnetic pole parts 523 h and the second claw-shaped magnetic pole parts 523 i are fixed by fixation members 521. The first pole core 52 h and the second pole core 52 i fixed by the fixation members 521 are rotatably supported on the housing 10 via bearings. The field windings 53 are arranged in the space between the first pole core 52 h and the second pole core 52 i. The field windings 53 are fixed to the boss part 17.

The magnetic flux radially flows in the disc parts 522 h and 522 i. The disc parts 522 h and 522 i have the arc-shaped groove portions 522 j and 522 k formed to extend in the circumferential direction from the portions connected to the outermost claw-shaped magnetic pole parts 523 h and 523 i as seen in the radial direction of the disc parts 522 h and 522 i. Accordingly, due to the groove portions 522 j and 522 k, the area of the cross section orthogonal to the flowing direction of the magnetic flux is decreased. That is, the cross sections of the outermost peripheral portions of the disc parts 522 h and 522 i connected to the claw-shaped magnetic pole parts 523 h and 523 i become smaller.

In the present embodiment, the relationship between the area A1 of the circle with a diameter equivalent to the outer diameter Dr of the pole cores 52 h and 52 i as the outer diameter of the rotor 50 and the cross-sectional area A2 of the portion with the minimum area of the cross section orthogonal to the flowing direction of the magnetic flux is set within the range of 0.2116<A2/A1<0.2809. The cross-sectional area A2 is obtained by multiplying the cross-sectional area A0 of the disc parts 522 h and 522 i having the groove portions 522 j and 522 k connected to the claw-shaped magnetic pole parts 523 h and 523 i by the number of pole pairs P.

<Operations and Advantageous Effects>

Even with the brushless structure, the rotary electrical machine drive system in the present embodiment can produce the same advantageous effects as those of the third embodiment.

Even with the brushless structure, the basic configuration of the field core is identical to those in the fourth to tenth embodiments. Accordingly, the configurations in the fourth to tenth embodiments are also applicable to a vehicle alternating-current power generator with a brushless structure. In this case, even with the brushless structure, the same advantageous effects as those of the fourth to tenth embodiments can be obtained.

Other Embodiments

The technique of the present disclosure is not limited to the foregoing embodiments. The technique of the present disclosure can be modified in various manners without deviating from the gist of the present disclosure.

For example, in the foregoing embodiments, the d-axis magnetic circuit 36 or 56 and part of the first and second magnet magnetic circuits 38, 39, 58, or 59 are shared. However, the d-axis magnetic circuit and all the first and second magnet magnetic circuits may be shared by embedding or placing the permanent magnets 34 or 54 in the d-axis magnetic circuit 36 or 56.

In a first modification example illustrated in FIG. 46, cylindrical permanents magnet 34A with magnetic poles at both axial ends are coaxially attached to the outer periphery of the boss part 321 having the d-axis magnetic circuit 36. Accordingly, the d-axis magnetic circuit 36 (see FIG. 8) and all the first and second magnet magnetic circuits 38A and 39A can be shared. The total radial cross-sectional area of the portions of the boss part 321 having the permanent magnets 34A is designated as A and the number of pole pairs of the rotary electrical machine as P. In this case, the axially extending iron core cross-sectional area Ab of a pair of NS poles of the boss part 321 is expressed as A/P.

Besides, permanent magnets can be embedded in or placed on the disc parts 322 a and 322 b (see FIG. 46) of the field core 32 having the d-axis magnetic circuit 36. In this case, the cross-sectional areas of the disc parts 322 a and 322 b are the cross-sectional areas of the portions of the disc parts 322 a and 322 b with the permanent magnets (disc part iron core portions).

<Aspects of the Present Disclosure>

A first rotary electrical machine drive system as an aspect of the technique of the present disclosure includes: a rotary electrical machine (1) having an annular stator (20) on which an armature winding (25) is wound and a rotor (30) on which a field winding (33) in wound and that is radially opposed to an inner peripheral side of the stator; and a control device (60) that controls electric current supplied to at least one of the field winding and the armature winding to generate torque in the rotor.

The rotor includes: a field core (32) having a cylindrical boss part (321, 321 a, 321 b) on which a field winding is wound and a plurality of claw-shaped magnetic pole parts (323, 323 a, 323 b) that are arranged on an outer peripheral side of the boss part and have magnetic poles different in polarity alternating in a circumferential direction; and permanent magnets (34, 34A) that are arranged with an axis of easy magnetization oriented in the circumferential direction between the circumferentially adjacent claw-shaped magnetic pole parts and have magnetic poles formed to match the alternating polarities of the claw-shaped magnetic pole parts produced by the magnetomotive force of the field winding.

In the first rotary electrical machine drive system, when an electrical load is connected to the rotor, the relationship between a permeance Prt of the d-axis magnetic circuit and a permeance Pst of a q-axis magnetic circuit (37) that is formed from electric current flowing in an armature winding and passes through a q axis shifted from the d axis at an electrical angle of 90° is set to satisfy Pst>Prt.

The control device performs phase control such that the rotary electrical machine performs either power running or regeneration.

According to this configuration, in the first rotary electrical machine drive system, the permanent magnets arranged between the circumferentially adjacent claw-shaped magnetic pole parts form two magnet magnetic circuits, that is, a first magnet magnetic circuit in which the magnetic flux interlinked with the stator flows and a second magnet magnetic circuit in which the magnetic flux passes through the boss part and returns to the rotor. When an electrical load is connected to the rotor, that is, when the field current is distributed by the control device to the field winding, the d-axis magnetic circuit is formed in which the magnetic flux formed by the magnetomotive force of the field winding flows through the boss part and the pair of claw-shaped magnetic pole parts of the field core, and the stator core. At this time, the flowing direction of the magnet magnetic flux in, of the two magnet magnetic circuits, the second magnet magnetic circuit in which the magnetic flux passes through the boss part and returns to the rotor is opposite to the flowing direction of the magnetic flux in the d-axis magnetic circuit. Accordingly, the magnetic flux of the magnet magnetic circuit is unlikely to flow due to the magnetic resistance being large. Therefore, in the first rotary electrical machine drive system, the relationship between the permeance Prt of the d-axis magnetic circuit and the permeance Pst of the q-axis magnetic circuit is set to satisfy Pst>Prt. This increases the magnet magnetic flux in, of the first and second magnet magnetic circuits, the first magnet magnetic circuit in which the first magnetic flux interlinked with the stator flows. Accordingly, the electric torque generated in the rotor can be significantly improved by the efficient use of the magnet magnetic flux.

The control device in the present disclosure performs phase control such that the rotary electrical machine performs either power running or regeneration. Specifically, when the rotary electrical machine conducts power running (acceleration and speed keeping) or regeneration (simultaneous braking and power generation), the maximum effective torque can be obtained by phase control. In this situation, reluctance torque is generated by applying field-weakening magnetic flux. Applying field-weakening magnetic flux to the d axis means applying the field-weakening magnetic flux to the field core connected to the d axis. That is, at the time of power distribution to the field winding, the saturation of the field core is decreased so that the magnetic force of the permanent magnets is not guided to the stator and is not effectively used. In this case, when the relationship in magnitude between the permeance Prt of the d-axis magnetic circuit and the permeance Pst of the q-axis magnetic circuit is satisfied, the field core is sufficiently saturated. Therefore, the field-weakening magnetic flux is not supplied to the field core so that the reluctance torque can be obtained with little regard to the field-weakening magnetic flux. Accordingly, the performance of power running and regeneration under phase control can be improved in a synergistic manner as compared to the case in which the technique of the present disclosure is applied to operations such as diode rectification and synchronous rectification using only the d axis.

In the present disclosure, the state where the rotor is under an electrical load refers to the state in which the field current If as rated current is distributed to the field winding in a range of 4 to 20 [A] that is usual for performance of a vehicle brush. With an improved structure of the brush, the field current If at that time (for example, 30 [A] or the like) can be used. In a configuration without limitation on the field current If such as a brush-less configuration, the required relationship Pst>Prt can be established by the larger field current If. Even with the known brush, the effect of satisfying the requirement 0.9<As/Ab<1.7 described later would be enormous in the sense of establishing the relationship Pst>Prt.

A second rotary electrical machine with a brushless structure as an aspect of the technique of the present disclosure includes: a brushless rotary electrical machine (2) having an annular stator (20) on which an armature winding (25) is wound, a rotor (30) radially opposed to an inner peripheral side of the stator, and a housing (10) that stores the stator and the rotor and has a boss part (17) on which a field winding (33) is wound; and a control device (60) that controls electric current supplied to at least one of the field winding and the armature winding to generate torque in the rotor.

The rotor includes: a field core (52) having a plurality of magnetic pole parts (52 n, 52 s) that is arranged on an outer peripheral side of the field winding and has magnetic poles different in polarity alternating in a circumferential direction; and permanent magnets (54) that are arranged with an axis of easy magnetization oriented in the circumferential direction between the circumferentially adjacent magnetic pole parts and have magnetic poles formed to match the alternating polarities of the magnetic pole parts produced by the magnetomotive force of the field winding.

In the second rotary electrical machine drive system, when an electrical load is connected to the rotor, the relationship between a permeance Prt of the d-axis magnetic circuit and a permeance Pst of a q-axis magnetic circuit (57) that is formed from electric current flowing in an armature winding and passes through a q axis shifted from the d axis at an electrical angle of 90° is set to satisfy Pst>Prt.

The control device performs phase control such that the rotary electrical machine performs either power running or regeneration.

According to this configuration, in the second rotary electrical machine drive system, the permanent magnets arranged between the circumferentially adjacent magnetic pole parts form two magnet magnetic circuits, that is, a first magnet magnetic circuit formed by the magnetic flux interlinked with the stator flows and a second magnet magnetic circuit that passes through the boss part and returns to the rotor. When an electrical load is connected to the rotor, that is, when the field current is distributed by the control device to the field winding, the d-axis magnetic circuit is formed in which the magnetic flux formed by the magnetomotive force of the field winding flows through the boss part and the pair of claw-shaped magnetic pole parts of the field core, and the stator core. At this time, the flowing direction of the magnet magnetic flux in, of the two magnet magnetic circuits, the second magnet magnetic circuit that passes through the boss part and returns to the rotor is opposite to the flowing direction of the magnetic flux in the d-axis magnetic circuit. Accordingly, the magnetic flux of the magnet magnetic circuit is unlikely to flow due to the magnetic resistance being large. Therefore, in the first rotary electrical machine drive system, the relationship between the permeance Prt of the d-axis magnetic circuit and the permeance Pst of the q-axis magnetic circuit is set to satisfy Pst>Prt. This increases the magnet magnetic flux in, of the first and second magnet magnetic circuits, the first magnet magnetic circuit in which the magnetic flux interlinked with the stator flows. Accordingly, the electric torque generated in the rotor can be significantly improved by the efficient use of the magnet magnetic flux.

In particular, the brushless rotary electrical machine is not subjected to current limitation due to a brush. Accordingly, it is possible to increase the value of the field current If that would be restricted due to a brush. This makes it possible to saturate the field circuit and use efficiently the magnet force even in the brushless rotary electrical machine. In addition, the independent electrical circuit distributes the field current to the field winding. Accordingly, with regard to centrifugal force as a weak point of the magnet-equipped Lundell rotor, the rear side of the magnetic pole parts is not subjected to the centrifugal force of the electrical circuit. This makes it possible to decrease stress resulting from centrifugal force.

The control device in the present disclosure performs phase control such that the rotary electrical machine performs either power running or regeneration. Specifically, when the rotary electrical machine conducts power running (acceleration and speed keeping) or regeneration (simultaneous braking and power generation), the maximum effective torque can be obtained by phase control. In this situation, reluctance torque is generated by applying field-weakening magnetic flux. Applying field-weakening magnetic flux to the d axis means applying the field-weakening magnetic flux to the field core connected to the d axis. That is, at the time of power distribution to the field winding, the saturation of the field core is decreased so that the magnetic force of the permanent magnets is not guided to the stator and is not effectively used. In this case, when the relationship in magnitude between the permeance Prt of the d-axis magnetic circuit and the permeance Pst of the q-axis magnetic circuit is satisfied, the field core is sufficiently saturated. Therefore, the field-weakening magnetic flux is not supplied to the field core so that the reluctance torque can be obtained with little regard to the field-weakening magnetic flux. Accordingly, the performance of power running and regeneration under phase control can be improved in a synergistic manner as compared to the case in which the technique of the present disclosure is applied to operations such as diode rectification and synchronous rectification using only the d axis.

In the present embodiment, the axially extending iron core cross-sectional area of a pair of NS poles of the boss part is designated as Ab and the magnetic flux density of the boss part with a magnetic field of 5000 [A/m] as B50. In addition, the residual magnetic flux density of the permanent magnet between the claw-shaped magnetic pole parts and between the magnetic pole parts is designated as Br and the cross-sectional area of the surface constituting the magnetic pole of the permanent magnet as Am. In the first or second rotary electrical machine drive system, the foregoing elements are set to satisfy the relationship 2×Br [T]×Am [mm²]<B50 [T]×Ab [mm²]. According to this configuration, in the rotary electrical machine of the present embodiment, the magnetic force generated by the permanent magnet can be absorbed by the d-axis magnetic circuit. This makes it possible to decrease the back-electromotive force and suppress the power generated in a high-speed rotation state without power distribution.

In the first or second rotary electrical machine drive system, the relationship between the permeance Prt of the d-axis magnetic circuit and the permeance Pst of the q-axis magnetic circuit is Pst:Prt=2n:1 (n is a real number of 1 or larger). According to this configuration, in the rotary electrical machine drive system of the present disclosure, the operation mode of the Lundell rotor under an electrical load can be brought closer to that of an IPM rotor. In addition, the saliency ratio ρ as the ratio (Lq/Ld) of the q-axis inductance Lq to the d-axis inductance Ld can be set to 2 or more. Accordingly, the Lundell rotor can output the same degree of reluctance torque as that in an IPM rotor.

A third rotary electrical machine drive system as an aspect of the present disclosure includes: a rotary electrical machine (1) having an annular stator (20) on which an armature winding (25) is wound and a rotor (30) on which a field winding (33) is wound and that is radially opposed to an inner peripheral side of the stator; and a control device (60) that controls electric current supplied to at least one of the field winding and the armature winding to generate torque in the rotor.

The rotor includes: a field core (32) having a cylindrical boss part (321, 321 a, 321 b) and a plurality of claw-shaped magnetic pole parts (323, 323 a, 323 b) that are arranged on an outer peripheral side of the boss part and have magnetic poles different in polarity alternating in a circumferential direction; a field winding (33) that is wound on the outer peripheral side of the boss part to generate a magnetomotive force by energization; and permanent magnets (34, 34A) that are arranged with an axis of easy magnetization oriented in the circumferential direction between the circumferentially adjacent claw-shaped magnetic pole parts and have magnetic poles formed to match the alternating polarities of the claw-shaped magnetic pole parts produced by the magnetomotive force of the field winding.

In the present disclosure, the surface area of the outer peripheral surface of the claw-shaped magnetic pole part is designated as As, and the axially extending iron core cross-sectional area of a pair of NS poles of the boss part as Ab.

In this case, in the third rotary electrical machine drive system, the relationship between the surface area As and the cross-sectional area Ab is set within the range of 0.9<As/Ab<1.7.

The control device performs phase control such that the rotary electrical machine performs either power running or regeneration.

According to this configuration, in the third rotary electrical machine drive system, the relationship between the surface area As of the outer peripheral surface of the claw-shaped magnetic pole part and the axially extending iron core cross-sectional area Ab of a pair of NS poles of the boss part is set within the range of 0.9<As/Ab<1.7. Accordingly, the magnet magnetic flux can be increased in, of the magnet magnetic circuits formed by the permanent magnets arranged between the circumferentially adjacent claw-shaped magnetic pole parts, the magnet magnetic circuit in which the magnet magnetic flux interlinked with the stator flows. This improves significantly the electric torque by the efficient use of the magnet magnetic flux. The permanent magnets arranged between the claw-shaped magnetic pole parts are conventionally used for the purposes of rectification of magnetic flux and prevention of leakage of magnetic flux. In contrast, in the present disclosure, the permanent magnets arranged between the claw-shaped magnetic pole parts are used like permanent magnets in an IPM rotor. This achieves increase of magnetic flux rather than prevention of leakage of magnetic flux. That is, the permanent magnets can act as a source for torque increase or a source for power increase.

The control device in the present disclosure performs phase control such that the rotary electrical machine performs either power running or regeneration. Specifically, when the rotary electrical machine conducts power running (acceleration and speed keeping) or regeneration (simultaneous braking and power generation), the maximum effective torque can be obtained by phase control. In this situation, reluctance torque is generated by applying field-weakening magnetic flux. Applying field-weakening magnetic flux to the d axis means applying the field-weakening magnetic flux to the field core connected to the d axis. That is, at the time of power distribution to the field winding, the saturation of the field core is decreased so that the magnetic force of the permanent magnets is not guided to the stator and is not effectively used. In this case, when the relationship in magnitude between the permeance Prt of the d-axis magnetic circuit and the permeance Pst of the q-axis magnetic circuit is set within a range of 0.9<As/Ab<1.7, the field core is sufficiently saturated. Therefore, the field-weakening magnetic flux is not supplied to the field core so that the reluctance torque can be obtained with little regard to the field-weakening magnetic flux. Accordingly, the performance of power running and regeneration under phase control can be improved in a synergistic manner as compared to the case in which the technique of the present disclosure is applied to operations such as diode rectification and synchronous rectification using only the d axis.

A fourth rotary electrical machine drive system of a brushless structure as an aspect of the technique of the present disclosure includes: a brushless rotary electrical machine (2) having an annular stator (20) on which an armature winding (25) is wound, a rotor (50) radially opposed to an inner peripheral side of the stator, and a housing (10) that stores the stator and the rotor and has a boss part (17) on which a field winding (33) is wound; and a control device (60) that controls electric current supplied to at least one of the field winding e and the armature winding to generate torque in the rotor.

The rotor includes: a field core (52) having a plurality of magnetic pole parts (523 h, 523 i) that is arranged on the outer peripheral side of the field winding and has magnetic poles different in polarity alternating in a circumferential direction; and permanent magnets (54) that are arranged with an axis of easy magnetization oriented in the circumferential direction between the circumferentially adjacent magnetic pole parts and have magnetic poles formed to match the alternating polarities of the magnetic pole parts produced by the magnetomotive force of the field winding.

In the present disclosure, the surface area of the outer peripheral surface of the claw-shaped magnetic pole part is designated as As, and the axially extending iron core cross-sectional area of a pair of NS poles of the boss part is designated as Ab.

In this case, in the fourth rotary electrical machine drive system, the relationship between the surface area As and the cross-sectional area Ab is set within a range of 0.9<As/Ab<1.7.

The control device performs phase control such that the rotary electrical machine performs either power running or regeneration.

According to this configuration, in the fourth rotary electrical machine drive system, the relationship between the surface area As of the outer peripheral surface of the magnetic pole part and the axially extending iron core cross-sectional area Ab of a pair of NS poles of the boss part is set within the range of 0.9<As/Ab<1.7. Accordingly, the magnet magnetic flux can be increased in, of the magnet magnetic circuits formed by the permanent magnets arranged between the circumferentially adjacent magnetic pole parts, the magnet magnetic circuit in which the magnet magnetic flux interlinked with the stator flows. This improves significantly the power generation performance by the efficient use of the magnet magnetic flux. The permanent magnets arranged between the magnetic pole parts are conventionally used for the purposes of rectification of magnetic flux and prevention of leakage of magnetic flux. In contrast, in the present disclosure, the permanent magnets arranged between the magnetic pole parts are used like permanent magnets in an IPM rotor. This achieves increase of magnetic flux rather than prevention of leakage of magnetic flux. That is, the permanent magnets can act as a source for torque increase or a source for power increase.

In the third or fourth rotary electrical machine drive system, the relationship between the boss part outer diameter Db and the rotor outer diameter Dr is set within the range of 0.46<Db/Dr<0.53. According to this configuration, in the rotary electrical machine drive system of the present embodiment, the boss part cross-sectional area falls within a range determined with maximum consideration given to counteraction of the magnet magnetic force against the magnetic force of the boss part. The magnetic force of the boss part enough to counteract the counteraction of the magnet magnetic force acts on the field core. At this time, with the root cross-sectional area of the claw-shaped magnetic pole part, the total magnetic force of the boss part and the total magnetic force of the permanent magnets can be passed to the stator.

In the third or fourth rotary electrical machine drive system, the residual magnetic flux density Br of the permanent magnet is set to 1 or more [T]. According to this configuration, in the rotary electrical machine drive system of the present embodiment, the foregoing operations and advantageous effects can be further effectively obtained.

In the first or second rotary electrical machine drive system, the parts having the d-axis magnetic circuit (36, 56) are formed from two kinds of materials different in the saturation flux density Bs. The claw-shaped magnetic pole parts or magnetic pole parts are formed from a material high in saturation flux density Bs, and the parts other than the claw-shaped magnetic pole parts or magnetic pole parts are formed from a material low in the saturation flux density Bs. According to this configuration, in the rotary electrical machine drive system of the present embodiment, the boss part becomes more quickly saturated in magnetic flux and more likely to change to the behavior of magnetic flux characteristics of an IPM rotor than the claw-shaped magnetic pole parts or magnetic pole parts. This makes it possible to improve the electric torque in a more reliable manner.

In the foregoing rotary electrical machine drive system, the material low in the saturation flux density Bs is higher in magnetic permeability than the material high in the saturation flux density Bs. According to this configuration, in the rotary electrical machine drive system of the present embodiment, the capability of absorbing the electromotive force can be enhanced at no load on the rotor.

In the third or fourth rotary electrical machine drive system, the field core has the decreased area of the cross section orthogonal to the flowing direction of the magnetic flux. In the third or fourth rotary electrical machine drive system, the relationship between the area A1 of the circle with a diameter equivalent to the outer diameter Dr of the rotor and the cross-sectional area A2 of the portion with the minimum area of the cross section orthogonal to the flowing direction of the magnetic flux is set within the range of 0.2116<A2/A1<0.2809. According to this configuration, in the rotary electrical machine drive system of the present embodiment, the field core has the decreased area of the cross section orthogonal to the flowing direction of the magnetic flux This changes the characteristics of the rotary electrical machine. That is, it is easy to form rotary electrical machines different in characteristics. Further, in the rotary electrical machine drive system of the present embodiment, the relationship between the area A1 of the circle with a diameter equivalent to the outer diameter Dr of the rotor and the cross-sectional area A2 of the portion with the minimum area of the cross section orthogonal to the flowing direction of the magnetic flux is set within the range of 0.2116<A2/A1<0.2809. This makes it possible to ensure the same magnetic relationship and producing the same advantageous effects as those in the case of setting the relationship between the outer diameter Db of the boss part and the outer diameter Dr of the rotor in the range of 0.46<Db/Dr<0.53.

The reference signs parenthesized suffixed to the names of the members and portions described in the following aspects of the present disclosure and in the claims indicate the correspondences with the specific members and portions in the foregoing exemplary embodiments. Accordingly, these reference signs have no influence on the configurations described in the claims.

REFERENCE SIGNS LIST

-   1, 2 . . . Rotary electrical machine -   10 . . . Housing -   17 . . . Boss part -   20 . . . Stator -   21 . . . Stator core -   25 . . . Armature winding -   30 . . . Rotor -   32 . . . Field core -   321 . . . Boss part -   321 a . . . First boss part -   321 b . . . Second boss part -   323 . . . Claw-shaped magnetic pole part -   323 a . . . First claw-shaped magnetic pole parts -   323 b . . . Second claw-shaped magnetic pole parts -   33 . . . Field winding -   34,34A . . . Permanent magnet -   36 . . . d-axis magnetic circuit -   37 . . . q-axis magnetic circuit -   38 . . . First magnet magnetic circuit -   39 . . . Second magnet magnetic circuit -   50 . . . Rotor -   52 . . . Field core -   52 n . . . N pole (magnetic pole part) -   52 s . . . S pole (magnetic pole part) -   53 . . . Field winding -   54 . . . Permanent magnet -   56 . . . d-axis magnetic circuit -   57 . . . q-axis magnetic circuit -   58 . . . First magnet magnetic circuit -   59 . . . Second magnet magnetic circuit -   60 . . . Control device 

The invention claimed is:
 1. A rotary electrical machine drive system comprising: a rotary electrical machine having an annular stator on which an armature winding is wound, and a rotor on which a field winding in wound and that is radially opposed to an inner peripheral side of the stator; and a control device that controls electric current supplied to at least one of the field winding and the armature winding to generate torque in the rotor, wherein, the rotor includes: a field core having a cylindrical boss part on which the field winding is wound and a plurality of claw-shaped magnetic pole parts that are arranged on the outer peripheral side of the boss part and have magnetic poles different in polarity alternating in a circumferential direction; and permanent magnets that are arranged with an axis of easy magnetization oriented in the circumferential direction between the circumferentially adjacent claw-shaped magnetic pole parts and have magnetic poles formed to match the alternating polarities of the claw-shaped magnetic pole parts produced by the magnetomotive force of the field winding, when an electrical load is connected to the rotor, a relationship between a permeance Prt of a d-axis magnetic circuit and a permeance Pst of a q-axis magnetic circuit that is formed from electric current flowing in the armature winding and passes through a q axis shifted from the d axis at an electrical angle of 90° is set to satisfy Pst>Prt, and the control device performs phase control such that the rotary electrical machine performs either power running or regeneration.
 2. The rotary electrical machine drive system comprising: a brushless rotary electrical machine having an annular stator on which an armature winding is wound, and a rotor radially opposed to an inner peripheral side of the stator, and a housing that stores the stator and the rotor and has a boss part on which a field winding is wound; and a control device that controls electric current supplied to at least one of the field winding and the armature winding to generate torque in the rotor, wherein, the rotor includes: a field core having a plurality of magnetic pole parts that is arranged on an outer peripheral side of the field winding and has magnetic poles different in polarity alternating in a circumferential direction; and permanent magnets that are arranged with an axis of easy magnetization oriented in the circumferential direction between the circumferentially adjacent magnetic pole parts and have a magnetic pole formed to match the alternating polarities of the magnetic pole parts produced by the magnetomotive force of the field winding, when an electrical load is connected to the rotor, a relationship between a permeance Prt of a d-axis magnetic circuit and a permeance Pst of a q-axis magnetic circuit that is formed from electric current flowing in the armature winding and passes through a q axis shifted from the d axis at an electrical angle of 90° is set to satisfy Pst>Prt, and the control device performs phase control such that the rotary electrical machine performs either power running or regeneration.
 3. The rotary electrical machine drive system according to claim 1, wherein, when an axially extending iron core cross-sectional area of a pair of NS poles of the boss part is designated as Ab and a magnetic flux density of the boss part with a magnetic field of 5000 [A/m] as B50, a residual magnetic flux density of the permanent magnet arranged between the claw-shaped magnetic pole parts as Br, and a cross-sectional area of a surface of the permanent magnet constituting the magnetic pole as Am, a relationship 2×Br×Am<B50×Ab is satisfied.
 4. The rotary electrical machine drive system according to claim 2, wherein, an axially extending iron core cross-sectional area of a pair of NS poles of the boss part is designated as Ab, a magnetic flux density of the boss part with a magnetic field of 5000 [A/m] as B50, a residual magnetic flux density of the permanent magnet arranged between the magnetic pole parts as Br, and a cross-sectional area of surface of the permanent magnet constituting the magnetic pole as Am, a relationship 2×Br×Am<B50×Ab is satisfied.
 5. The rotary electrical machine drive system according to claim 1, wherein, a ratio of the permeance Prt of the d-axis magnetic circuit to the permeance Pst of the q-axis magnetic circuit is set to Pst:Prt=2n:1, n being a real number of 1 or larger.
 6. A rotary electrical machine drive system comprising: a rotary electrical machine having an annular stator on which an armature winding is wound and a rotor on which a field winding in wound and that is radially opposed to an inner peripheral side of the stator; and a control device that controls electric current supplied to at least one of the field winding and the armature winding to generate torque in the rotor, wherein, the rotor includes: a field core having a cylindrical boss part and a plurality of claw-shaped magnetic pole parts that are arranged on an outer peripheral side of the boss part and have magnetic poles different in polarity alternating in a circumferential direction; a field winding that is wound on the outer peripheral side of the boss part to generate a magnetomotive force by energization; and permanent magnets that are arranged with an axis of easy magnetization oriented in the circumferential direction between the circumferentially adjacent claw-shaped magnetic pole parts and have magnetic poles formed to match the alternating polarities of the claw-shaped magnetic pole parts produced by the magnetomotive force of the field winding, when a surface area of the outer peripheral surface of the claw-shaped magnetic pole part is designated as As, and an axially extending iron core cross-sectional area of a pair of NS poles of the boss part as Ab, a relationship between the surface area As and the cross-sectional area Ab is set within a range of 0.9<As/Ab<1.7, and the control device performs phase control such that the rotary electrical machine performs either power running or regeneration.
 7. A rotary electrical machine drive system comprising: a brushless rotary electrical machine having an annular stator on which an armature winding is wound, a rotor radially opposed to an inner peripheral side of the stator, and a housing that stores the stator and the rotor and has a boss part on which a field winding is wound; and a control device that controls electric current supplied to at least one of the field winding and the armature winding to generate torque in the rotor, wherein, the rotor includes: a field core having a plurality of magnetic pole parts that is arranged on an outer peripheral side of the field winding and has magnetic poles different in polarity alternating in a circumferential direction; and permanent magnets that are arranged with an axis of easy magnetization oriented in the circumferential direction between the circumferentially adjacent magnetic pole parts and have magnetic poles formed to match the alternating polarities of the magnetic pole parts produced by the magnetomotive force of the field winding, when a surface area of the outer peripheral surface of the magnetic pole part is designated as As, and an axially extending iron core cross-sectional area of a pair of NS poles of the boss part as Ab, a relationship between the surface area As and the cross-sectional area Ab is set within a range of 0.9<As/Ab<1.7, and the control device performs phase control such that the rotary electrical machine performs either power running or regeneration.
 8. The rotary electrical machine drive system according to claim 6, wherein, a relationship between an outer diameter Db of the boss part and an outer diameter Dr of the rotor is set within a range of 0.46<Db/Dr<0.53.
 9. The rotary electrical machine drive system according to claim 6, wherein the residual magnetic flux density Br of the permanent magnet is set to 1 or more [T].
 10. The rotary electrical machine drive system according to claim 1, wherein, parts with the d-axis magnetic circuit are formed from two kinds of materials different in saturation flux density Bs, and the claw-shaped magnetic pole parts are formed from a material high in the saturation flux density Bs, and the parts other than the claw-shaped magnetic pole parts are formed from a material low in saturation flux density Bs.
 11. The rotary electrical machine drive system according to claim 2, wherein, parts with the d-axis magnetic circuit are formed from two kinds of materials different in saturation flux density Bs, and the magnetic pole parts are formed from a material high in the saturation flux density Bs, and the parts other than the magnetic pole parts are formed from a material low in saturation flux density Bs.
 12. The rotary electrical machine drive system according to claim 10, wherein, the material low in the saturation flux density Bs is higher in magnetic permeability than the material high in the saturation flux density Bs.
 13. The rotary electrical machine drive system according to claim 1, wherein, the field core has a decreased area of cross section orthogonal to the flowing direction of a magnetic flux, and a relationship between an area A1 of a circle with a diameter equivalent to the outer diameter Dr of the rotor and a cross-sectional area A2 of a portion with a minimum area of the cross section orthogonal to the flowing direction of the magnetic flux is set within a range of 0.2116<A2/A1<0.2809. 